Surface position detection device and exposure apparatus and exposure method achieved by utilizing detection device

ABSTRACT

A surface position detection device that detects the surface position of a detection target surface (Wa) is provided with a projection system ( 1˜6 ) provided to project a light flux onto the detection target surface from a diagonal direction and a light-receiving system ( 7˜14 ) provided to receive a light flux having been reflected at the detection target surface. A means for light flux deflection ( 6, 7 ) which includes an even number of reflection surfaces to allow an incident light flux to exit at an angle not parallel to the incident light flux is provided, at least, either in the optical path of the projection system or the optical path of the light-receiving system. The surface position of the detection target surface is detected based upon an output from the light-receiving system. Any deterioration in the detection accuracy attributable to vibration from the outside, temperature fluctuations and the like can be successfully prevented, and the structure essentially frees the optical systems from any structural and positional restrictions imposed by the proximity of the detection target surface.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a surface position detectiondevice and an exposure apparatus and an exposure method achieved byutilizing the detection device. More specifically, it relates todetection of the surface position of a photosensitive substrate in aprojection exposure apparatus which is employed to transfer a maskpattern onto the photosensitive substrate in the lithography processimplemented to manufacture a micro device such as a semiconductorelement, a liquid crystal display element, an image-capturing element(such as a CCD) and a thin film magnetic head.

[0002] Surface position detection devices ideal in application inprojection exposure apparatuses in the known art include the obliqueincidence-type surface position detection device disclosed by theapplicant of the present invention in Japanese Unexamined PatentPublication No. 42205/1981. In this surface position detection device,detection light is irradiated from a diagonal direction onto asemiconductor wafer set at a position which allows a mask pattern to betransferred onto it through a projection lens. More specifically, a slitpattern is projected onto the detection target surface, i.e., thesurface of the semiconductor wafer, by ensuring that the direction alongwhich the long side of the slit pattern extends is perpendicular to theentrance plane (the plane formed of the incident light and the reflectedlight). Then, by condensing the reflected light, a pattern image isreformed on a detection surface of a means for detection constituted ofa photoelectric conversion element and the position at which the patternimage is formed on the detection surface is detected.

[0003] In the surface position detection device structured as describedabove, when the surface of the semiconductor wafer constituting thedetection target surface becomes displaced along the vertical direction(displaced along the optical axis of the projection lens), the slitreflection light entering the means for detection becomes shiftedlaterally along the widthwise direction (the direction along which theshort side extends) in correspondence to the vertical displacement.Accordingly, the position of the surface of the semiconductor waferalong the vertical direction is detected based upon the degree of thelateral shift. Thus, based upon the results of the detection, a decisionis made as to whether or not the wafer surface is aligned at the focusreference position of the projection lens, i.e., whether or not thewafer surface is aligned on a plane that is conjugate with the surfaceof the mask pattern projected by the projection lens.

[0004] In addition, Japanese Unexamined Patent Publication No.97045/1994 filed by the applicant of the present invention discloses animprovement on the oblique incidence-type surface position detectiondevice described above, which is capable of performing positiondetection over a wide area of the detection target surface. This surfaceposition detection device is provided with a projection optical systemthat projects an image of a specific pattern formed at a first surfaceonto a wafer surface constituting a detection target surface and acondenser optical system that condenses a light flux having beenreflected at the detection target surface and forms an image of thespecific pattern on a second surface at which a light-receiving slit isformed. In addition, shine-proofing is achieved for the first surfaceand the detection target surface with respect to the projection opticalsystem and shine-proofing is achieved for the detection target surfaceand the second surface with respect to the condenser optical system.

[0005] In this surface position detection device, the projection opticalsystem and the condenser optical system each achieve bilateraltelecentricity, to assure that uniform magnification is achieved at thevarious points on the first surface and the various corresponding pointson the detection target surface over the entire surface areas and thatuniform magnification is achieved at various points on the detectiontarget surface and various corresponding points on the second surfaceover the entire surface areas. By assuming these structural features, auniform degree of detection accuracy is achieved over the entiredetection area on the detection target surface through a detectionmethod based upon the principle of photoelectric microscopy in which theimage of the specific pattern formed on the second surface and thelight-receiving slit are scanned relative to each other to synchronouslydetect light modulation signals.

SUMMARY OF THE INVENTION

[0006] In principle, it is necessary to increase the angle of incidenceof a light flux entering the detection target surface (to set the angleof incidence as close as possible to 90°) in order to improve theaccuracy with which the surface position of the detection target surfaceis detected. In such a case, the projection optical system and thecondenser optical system will be set close to the detection targetsurface, creating restrictions attributable to the proximity of thedetection target surface on the structures and the positions of theseoptical systems. In particular, the components of the optical systemsare bound to become large if it is necessary to detect the surfaceposition over a wide range of the detection target surface, resulting infurther restrictions imposed with regard to the structures and thepositions. If the work distances WD of the projection optical system andthe condenser optical system are both set large to eliminate suchrestrictions on the structures and the positions, larger components arerequired to constitute the optical systems. Thus, structural andpositional restrictions cannot be effectively eliminated by setting thework distances of optical systems to large values.

[0007] The structural and positional restrictions mentioned above may besuccessfully eliminated by providing a mirror in the optical path of theprojection optical system and a mirror in the optical path of thecondenser optical system, which greatly bend the optical path of theincident light flux entering the detection target surface and theoptical path of the reflected light flux originating from the detectiontarget surface to allow the projection optical system and the condenseroptical system to be set over distances from the detection targetsurface, as disclosed in Japanese Examined Patent Publication No.39955/1995 filed by the applicant of the present invention (see FIG. 4in the publication). Alternatively, as disclosed in the same publication(see FIG. 6 in the publication), prisms each having a pair of totalreflection surfaces which extend parallel to each other may be providedin the optical path of the projection optical system and the opticalpath of the condenser optical system, to cause parallel displacement ofthe optical path of the incident light flux entering the detectiontarget surface and the optical path of the reflected light fluxoriginating from the detection target surface and allow the projectionoptical system and the condenser optical system to be set over distancesfrom the detection target surface.

[0008] However, changes are bound to occur in the angles of inclinationof the reflection surfaces of the mirrors provided in the optical paths,due to displacement and distortion of the mirror holding membersattributable to vibration from the outside, temperature fluctuations andthe like. In such a case, a problem occurs in that the angle ofincidence and the entry position of the light flux entering thedetection target surface and the angle of incidence and the entryposition of the light flux entering the detection surface (the secondsurface) change to result in poor detection accuracy for detecting andthe surface position of the detection target surface. If, on the otherhand, the structure provided with prisms each having a pair of totalreflection surface of extending parallel to each other is adopted, thedetection accuracy is hardly reduced due to vibration from the outside,temperature fluctuations and the like. However, since these prismsretain parallelism between the optical path of the incident light fluxand the optical path of the exiting light flux and they do not deflectthe light fluxes at all, the projection optical system and the condenseroptical system must distend on both sides radially along the detectiontarget surface and thus, the structural and positional restrictions arenot fully eliminated.

[0009] An object of the present invention, which has been completed byaddressing the problems of the related art discussed above, is toprovide a surface position detection device in which deterioration inthe detection accuracy attributable to vibration from the outside,temperature fluctuations and the like can be successfully preventedessentially without having to conform to any restrictions imposed by theproximity of the detection target surface on the structures and thepositions of the optical systems. Another object of the presentinvention is to provide an exposure apparatus and an exposure methodthat achieve highly accurate alignment of a patterned surface of a maskand an exposure target surface of a photosensitive substrate relative tothe projection optical system by utilizing the surface positiondetection device according to the present invention.

[0010] In order to achieve the objects described above, in a firstaspect of the present invention, a surface position detection devicethat detects the surface position of a detection target surfacecomprising a projection system that projects a light flux from adiagonal direction onto the detection target surface and alight-receiving system that receives a light flux having been reflectedat the detection target surface, with a means for light flux deflectionhaving an even number of reflection surfaces to cause an incident lightflux to be emitted at an angle not parallel to the incident light fluxprovided, at least, either in the optical path of the projection systemor the optical path of the light-receiving system and the surfaceposition of the detection target surface is detected based upon anoutput from the light-receiving system is provided.

[0011] In a desirable mode of the first aspect of the present invention,the projection system is provided with a projection optical system thatforms a primary image of a specific pattern on the detection targetsurface and the light-receiving system is provided with a condenseroptical system that forms a secondary image of the specific pattern bycondensing a light flux having been reflected at the detection targetsurface and a detection unit that detects the secondary image of thespecific pattern formed via the condenser optical system, with thesurface position of the detection target surface is detected based uponan output from the detection unit.

[0012] In addition, in a desirable mode of the first aspect of thepresent invention, the means for light flux deflection is provided witha prism having a pair of reflection surfaces which are not parallel toeach other formed therein. When this structure is adopted, the prismshould have a first transmission surface through which an incident lightflux is transmitted, a first reflection surface at which the light fluxhaving been transmitted through the first transmission surface andpropagated through the inside of the prism is reflected, a secondreflection surface at which the light flux having been reflected at thefirst reflection surface and having been propagated through the insideof the prism is reflected along an optical path intersecting the opticalpath of the light flux having been transmitted through the firsttransmission surface and a second transmission surface through which thelight flux having been reflected at the second reflection surfacepropagated through the inside of the prism is transmitted.

[0013] Furthermore, the angle formed by the first reflection surface andthe second reflection surface should be set within a range of 40° orgreater and less than 45°. The prism should be preferably constituted ofa low-dispersion optical material achieving an Abbe number of 65 orhigher. It is also desirable that the prism be constituted of an opticalmaterial having a coefficient of thermal expansion equal to or lowerthan 1 ppm/K, which does not expand readily in heat.

[0014] In another desirable mode of the first aspect of the invention,the means for light flux deflection is provided with a pair ofreflecting mirrors which are not parallel to each other and holdingmembers each interfitted with one of the pair of reflecting mirrors tohold the reflecting mirror. In this structure, the holding membersshould be constituted of a material having a coefficient of thermalexpansion equal to or lower than 1 ppm/K, which does not expand readilyin heat.

[0015] In a second aspect of the present inventions an exposureapparatus that performs projection exposure of a pattern on a mask ontoa photosensitive substrate via a projection optical system, comprising asurface position detection device in the first aspect of the presentinvention that detects the surface position of the pattern surface ofthe mask or the exposure target surface of photosensitive substraterelative to the projection optical system as the surface position of adetection target surface and a means for alignment that aligns thepattern surface at the mask or the exposure target surface of thephotosensitive substrate relative to the projection optical system basedupon the results of a detection performed by the surface positiondetection device, is provided.

[0016] In a third aspect of the present invention, an exposure methodfor implementing projection exposure of a pattern on a mask onto aphotosensitive substrate via a projection optical system, comprising adetection step in which the surface position of the pattern surface atthe mask or the exposure target surface of the photosensitive substraterelative to the projection optical system is detected as the surfaceposition of a detection target surface by employing a surface positiondetection device in the first aspect of the invention and an alignmentstep in which the pattern surface at the mask or the exposure targetsurface of the photosensitive substrate is aligned relative to theprojection optical system based upon the results of a detectionperformed in the detection step, is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other features of the invention and the concomitantadvantages will be better understood and appreciated by persons skilledin the field to which the invention pertains in view of the followingdescription given in conjunction with the accompanying drawings whichillustrate preferred embodiments.

[0018]FIG. 1 is a schematic block diagram of a projection exposureapparatus having the surface position detection device in an embodimentof the present invention;

[0019]FIG. 2 is an optical path diagram illustrating that the projectionoptical system and the condenser optical system in FIG. 1 both achievebilateral telecentricity;

[0020]FIG. 3 is a perspective illustrating a primary image of thelattice pattern 3 a formed on the detection target surface Wa;

[0021]FIG. 4 schematically illustrates the structure of thelight-receiving slit S having five rectangular openings Sa1˜Sa5extending along direction X in narrow strips;

[0022]FIG. 5 shows five silicon photodiodes PD1˜PD5 provided on thelight-receiving surface 14 a of the light-receiving unit 14 to opticallycorrespond to the openings Sa1˜Sa5 of the light-receiving slit S;

[0023]FIG. 6 shows the relationship between the angle of intersectionformed by the pair of reflection surfaces at the pentaprism 6 in FIG. 1and the angle of deflection;

[0024]FIG. 7 schematically illustrates the structure of an essentialportion of a projection exposure apparatus having a surface positiondetection device achieved as a variation of the first embodiment;

[0025]FIG. 8 schematically illustrates the structure of a variation ofthe means for light flux deflection; and

[0026]FIG. 9 schematically illustrates the structure of the holdingmembers in FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0027] The surface position detection device according to the presentinvention includes a means for light flux deflection provided either inthe optical path of a projection system that projects a light flux ontoa detection target surface from a diagonal direction or the optical pathof a light-receiving system that receives a light flux having beenreflected at the detection target surface and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglenot parallel to the incident light flux. In a typical implementationmode of the present invention, in which the projection system isprovided with a projection optical system that forms a primary image ofa specific pattern onto the detection target surface and thelight-receiving system is provided with a condenser optical system thatforms a secondary image of the specific pattern by condensing a lightflux having been reflected at the detection target surface, the meansfor light flux deflection is provided both in the optical path betweenthe projection optical system and the detection target surface and inthe optical path between the condenser optical system and the detectiontarget surface.

[0028] In a more specific example, by forming a reflecting film at apair of side surfaces of a pentagonal prism facing opposite each other,a means for light flux deflection is realized in the form of a prismhaving a pair of reflection surfaces formed therein which are notparallel to each other. In this specification, the pentagonal prismmentioned above is referred to as a pentaprism. An incident light fluxentering the pentaprism is directly transmitted through a firsttransmission surface and is then propagated through the inside of theprism before it is reflected at a first reflection surface. The lightflux having been reflected at the first reflection surface andpropagated through the inside of the prism is then reflected at a secondreflection surface along the optical path intersecting the optical pathof the light flux having been transmitted through the first transmissionsurface. The light flux having been reflected at the second reflectionsurface and having been propagated through the inside of the prism isallowed to be directly transmitted through a second transmission surfaceand exit the pentaprism. Thus, the incident light flux having enteredthe pentaprism provided with a pair of reflection surfaces set toachieve an angle Ψ is deflected by the angle Φ before it is allowed toexit.

[0029] As is to be detailed later, at the pentaprism with its angle ofdeflection Φ univocally determined in correspondence to the angle ofintersection Ψ of a pair of reflection surfaces, a pair of reflectionsurfaces are provided by forming a reflecting film at two side surfacesof the pentagonal prism facing opposite each other. Thus, the angle ofintersection Ψ formed by the pair of reflection surfaces essentiallydoes not change due to vibration from the outside, temperaturefluctuations and the like and, as a result, the angle of deflection Ψdoes not change either. Consequently, even when the pentaprism becomestilted by a slight degree within the plane of incidence (the plane thatcontains the incident light flux and exiting light flux entering and theexiting the pentaprism) due to displacement and deformation of theholding member attributable to vibration from the outside, temperaturefluctuations and the like, the relationship between the angularpositions of the pair of reflection surfaces, (i.e., the angle ofintersection Ψ) remains unchanged, and the angle of deflection Φ of theprism, too, remains constant. In other words, the direction in which theexiting light flux advances remains unchanged, and the angle ofincidence of the light flux entering the detection target surface or thelight-receiving surface, too, remains constant. As a result, hardly anychange occurs in the angle of incidence and the entry position at thedetection target surface or the light-receiving surface, which makes itpossible to successfully prevent occurrence of a detection errorattributable to vibration from the outside, temperature fluctuations andthe like.

[0030] In addition, since the optical path of the incident light fluxentering the detection target surface and the optical path of thereflected light flux originating from the detection target surface aregreatly deflected by the pentaprisms provided in the optical pathbetween the projection optical system and the detection target surfaceand the optical path between the condenser optical system and thedetection target surface according to the present invention, theprojection optical system and the condenser optical system can be setover distances from the detection target surface to essentiallyeliminate restrictions imposed by the proximity of the detection targetsurface on the structures and the positions of the optical systems.

[0031] As described above, the surface position detection deviceaccording to the present invention successfully prevents anydeterioration in the detection accuracy attributable to vibration fromthe outside, temperature fluctuations and the like, essentially withouthaving to conform to any restrictions imposed by the proximity of thedetection target surface on the structures and the positions of theoptical systems.

[0032] In addition, by utilizing the surface position detection deviceaccording to the present invention to detect the surface position of thephotosensitive substrate relative to a projection optical system in aprojection exposure apparatus, highly accurate alignment of the maskpattern surface and the exposure target surface of the photosensitivesubstrate relative to the projection optical system is achieved,essentially without being affected by vibration of the projectionexposure apparatus, the ambient air temperature fluctuations and thelike. As a result, it becomes possible to manufacture appropriate microdevices by employing the projection exposure apparatus provided with thesurface position detection device according to the present invention.

[0033] Embodiments of the present invention are now explained inreference to the attached drawings.

[0034]FIG. 1 schematically illustrates the structure of a projectionexposure apparatus provided with the surface position detection devicein an embodiment of the present invention and FIG. 2 is an optical pathdiagram illustrating that the projection optical system and thecondenser optical system in FIG. 1 both achieve bilateraltelecentricity. It is to be noted that in FIG. 1, the Z axis is setparallel to an optical axis AX of a projection optical system PL, the Yaxis is set parallel to the surface of the sheet on which FIG. 1 isdrawn within a plane perpendicular to the optical axis AX and the X axisis set perpendicular to the surface of the drawing sheet. In thisembodiment, the surface position detection device according to thepresent invention is utilized in a detection of the surface position ofa photosensitive substrate in the projection exposure apparatus.

[0035] The projection exposure apparatus in the figure is provided withan illumination system IL that evenly illuminates a reticle Rconstituting a mask at which a specific pattern is formed withilluminating light (exposing light) emitted from an exposing lightsource (not shown). The reticle R is held parallel to the XY plane on areticle stage (not shown) via a reticle holder RH. The reticle stage iscapable of making two-dimensional movement along the reticle surface(i.e., the XY plane) when driven by a drive system (not shown), and itspositional coordinates are measured by a reticle interferometer (notshown) to enable positional control.

[0036] Light originating from the pattern formed at the reticle R formsa reticle pattern image on a surface (exposure target surface) Wa of awafer W constituting the photosensitive substrate via the projectionoptical system PL. The wafer W is placed on a wafer holder 21 which, inturn, is supported by a holder supporting mechanism 22. The holdersupporting mechanism 22 supports the wafer holder 21 at three supportpoints 22 a˜22 c (FIG. 1 and only shows two support points 22 a and 22b) that can move along the vertical direction (direction Z) inconformance to the control implemented by a holder drive unit 23.

[0037] Thus, the holder drive unit 23 controls vertical movements of theindividual support points 22 a˜22 c of the holder supporting mechanism22 to allow the wafer holder 21 to be leveled and to move alongdirection Z (the focusing direction) and ultimately to allow the wafer Wto be leveled and to move along direction Z. The wafer holder 21 and theholder supporting mechanism 22 are supported by a wafer stage (notshown). The wafer stage, which is driven by a drive system (not shown),is capable of making two-dimensional movement along the wafer surface(i.e., the XY plane) and rotating around the Z axis, and its positionalcoordinates are measured by a wafer interferometer (not shown) to enablepositional control.

[0038] In order to ensure that a circuit pattern provided on the patternsurface of the reticle R is successfully transferred to the individualexposure areas of the exposure target surface Wa of the wafer W, it isnecessary to align the current exposure area at the exposure targetsurface Wa within the width of the depth of focus with respect to theimage-forming plane at which at an image is formed through theprojection optical system PL for each exposure operation performed totransfer the circuit pattern onto a given exposure area. This alignmentmay be achieved by first accurately detecting the surface positions ofvarious points in the current exposure area, i.e., the surface positionsalong the optical axis AX of the projection optical system PL and thenleveling and moving the wafer holder 21 along direction Z and,ultimately, leveling and moving the wafer W along direction Z so as tocontain the exposure target surface Wa within the range of the width ofthe depth of focus of the projection optical system PL.

[0039] Accordingly, the projection exposure apparatus in the embodimentis provided with a surface position detection device that detectssurface positions at various points in the current exposure area of theexposure target surface Wa. In FIG. 1, the surface position detectiondevice in the embodiment is provided with a light source 1 that suppliesdetection light. Under normal circumstances, the surface Wa of the waferW constituting the detection target surface is covered with a thin filmsuch as a resist. Thus, it is desirable that the light source 1 is awhite light source that emits white light having a large wavelengthrange, to reduce the degree of the effect of the interferenceattributable to the thin film. It is to be noted that the light source 1may be constituted of a light emitting diode or the like that supplieslight in a wavelength band that does not manifest a high degree ofphotosensitivity to the resist.

[0040] A divergent light flux from the light source 1 is first convertedto a roughly collimated light beam via a condenser lens 2 and thenenters a deflecting prism 3. The deflecting prism 3 deflects the roughlycollimated light flux from the condenser lens 2 along direction −Zthrough refraction. In addition, at the exit side of the deflectingprism 3, a transmission-type lattice pattern 3 a having narrowtransmission portions extending along direction X and narrow lightblocking portions extending along direction X provided alternately toeach other at a constant pitch is formed. It is to be noted that insteadof such a transmission-type lattice pattern, a reflection-typediffraction grating with indentations and projections may be used or areflection-type lattice pattern having reflection portions andnon-reflection portions formed alternately may be utilized.

[0041] The light that has been transmitted through the transmission-typelattice pattern 3 a enters a projection optical system (4, 5) providedalong an optical axis AX1 parallel to the optical axis AX of theprojection optical system. The projection optical system (4, 5) isconstituted of a projection condenser lens 4 and a projection objectivelens 5. The light flux having travelled through the projection opticalsystem (4, 5) then enters a pentaprism 6. The pentaprism 6 is adeflecting pentagonal prism with its longer axis running in direction Xand is provided with a first transmission surface 6a through which lighthaving entered along the optical axis AX1 is directly transmittedwithout becoming refracted. In other words, the first transmissionsurface 6 a is set perpendicular to the optical axis AX1. The lighthaving been transmitted through the first transmission surface 6 a andpropagated through the inside of the pentaprism 6 along the optical axisAX1 is first reflected at a first reflection surface 6 b and thenreflected again at a second reflection surface 6 c along an optical axisAX2.

[0042] The light having been reflected at the second reflection surface6 c and propagated through the inside of the pentaprism 6 along theoptical axis AX2 is directly transmitted through a second transmissionsurface 6 d without becoming refracted. In other words, the secondtransmission surface 6 d is set perpendicular to the optical axis AX2.The pentaprism 6 is constituted of a low-dispersion optical materialwhich does not readily expand when heated such as quartz glass, and areflecting film constituted of aluminum, silver or the like is formedboth at the first reflection surface 6 b and the second reflectionsurface 6 c.

[0043] Thus, the light having entered in direction −Z along the opticalas AX1 is greatly deflected at the pentaprism 6 and reaches thedetection target surface Wa at a required angle of incidence along theoptical axis AX2. The direction in which the optical axis AX2 extends isset and, therefore, the angle of deflection achieved at the pentaprism6, too, is set so as to ensure a sufficiently large angle of incidenceat the detection target surface Wa at this time. As described above, thepentaprism 6 constitutes a means for light flux deflection having a pairof reflection surfaces to allow the incident light flux to exit at anangle not parallel to the incident light flux. It is to be noted that adetailed explanation on the structure assumed by the pentaprism 6 andits effects is to be given later.

[0044] The device assumes a structure in which the projection opticalsystem (4, 5) sets the surface at which the lattice pattern 3 a isformed (i.e., the exit surface of the deflecting prism 3) and thedetection target surface Wa conjugate with each other when the detectiontarget surface Wa is aligned with the image-forming plane of theprojection optical system PL. In addition, shine-proofing is achievedfor the surface at which the lattice pattern 3 a is formed and thedetection target surface Wa with respect to the projection opticalsystem (4, 5). As a result, the light originating from the latticepattern 3 a travels through the projection optical system (4, 5) andforms an image over the entire pattern image-forming plane of thedetection target surface Wa with accuracy.

[0045] As indicated by the dotted line representing its optical path inFIG. 2, the projection optical system (4, 5) constituted of theprojection condenser lens 4 and the projection objective lens 5 is aso-called bilateral telecentric optical system. Thus, uniformmagnification is achieved at various points on the surface at which thelattice pattern 3 a is formed and at various corresponding points on thedetection target surface Wa over the entire surfaces. As shown in FIG.3, a primary image of the lattice pattern 3 a is formed with a highdegree of accuracy over the entirety of the detection target surface Wa.

[0046] To continue with the explanation in reference to FIG. 1 again,the light having been reflected at the detection target surface Waenters a condenser optical system (8, 9) via a pentaprism 7 assuming astructure identical to that of the pentaprism 6. Namely, the lighthaving been reflected at the detection target surface Wa enters thepentaprism 7 along an optical axis AX3 symmetrical to the optical axisAX2 relative to the optical axis AX of the projection optical system PL.At the pentaprism 7, light having been transmitted through a firsttransmission surface 7 a perpendicular to the optical axis AX3 issequentially reflected at a first reflection surface 7 b and a secondreflection surface 7 c and then reaches a second transmission surface 7d along an optical axis AX4 extending along direction Z. Light havingbeen transmitted through the second transmission surface 7 dperpendicular to the optical axis AX4 enters the condenser opticalsystem (8, 9) in direction+Z along the optical axis AX4.

[0047] The condenser optical system (8, 9) is constituted of alight-receiving objective lens 8 and a light-receiving condenser lens 9.An oscillating mirror 10 constituting a means for scanning is providedin the optical path located between the light-receiving objective lens 8and the light-receiving condenser lens 9. Thus, the light having enteredthe light-receiving objective lens 8 along the optical axis AX4 becomesdeflected via the oscillating mirror 10 and reaches the light-receivingcondenser lens 9 along an optical axis AX5. It is to be noted that whilethe oscillating mirror 10 is set roughly at the pupil surface of thecondenser optical system (8, 9) in this embodiment, the presentinvention is not restricted by these particulars and the oscillatingmirror 10 may be set at any position within the optical path between thedetection target surface Wa and the light-receiving surface.

[0048] The light having traveled through the condenser optical system(8, 9) then enters the swing correction prism 1I assuming a structureidentical to that of the deflecting prism 3. The device assumes astructure in which the condenser optical system (8, 9) sets thedetection target surface Wa and an entry surface 11 a of the swingcorrection prism 11 conjugate with each other when the detection targetsurface Wa is aligned with the image-forming plane of the projectionoptical system PL. As a result, a secondary image of the lattice pattern3 a is formed at the entry surface 11 a of the swing correction prism11.

[0049] It is to be noted that a light-receiving slit S constituting ameans for light blocking is provided at the entry surface 11 a of theswing correction prism 11. As shown in FIG. 4, the light-receiving slitS is provided with a plurality of, e.g., five rectangular openingsSa1˜Sa5 extending along direction X in narrow strips. The reflectedlight from the detection target surface Wa having traveled through thecondenser optical system (8, 9) passes through the individual openingsSa1˜Sa5 at the light-receiving slit S to enter the swing correctionprism 11.

[0050] The number of openings Sa at the light-receiving slit S matchesthe number of detection points on the detection target surface Wa.Namely, in FIG. 3 illustrating a primary image of the lattice pattern 3a formed the detection target surface Wa, detection points (detectionareas) Da1˜Da5 on the detection target surface Wa optically correspondto the openings Sa1˜Sa5 respectively at the light-receiving slit S inFIG. 4. As a result, the number of detection points on the detectiontarget surface Wa can be increased simply by increasing the number ofopenings Sa, without complicating the structure of the detection deviceitself.

[0051] It is to be noted that shine-proofing is achieved for theimage-forming plane at which an image is formed by the projectionoptical system PL and the entry surface 11 a of the swing correctionprism 11 with respect to the condenser optical system (8, 9). Thus, whenthe detection target surface Wa is aligned with the image-forming plane,the light originating from the lattice pattern 3 a travels through thecondenser optical system (8, 9) to reconstitute an image with accuracyover the entire pattern image-forming area on the prism entry surface 11a.

[0052] In addition, as indicated by the dotted line representing theoptical path in FIG. 2, the condenser optical system (8, 9) isconstituted of a bilateral telecentric optical system. Thus, a uniformmagnification is achieved at various points on the detection targetsurface Wa and the various corresponding points on the prism entrysurface 11 a. Consequently, a secondary image of the lattice pattern 3 ais formed with accuracy over the entire entry surface 11 a of the swingcorrection prism 11.

[0053] If the light-receiving surface is set at the entry surface 11 aof the swing correction prism 11, the angle of incidence of a light fluxentering the light-receiving surface increases because of a large angleof incidence θ of the light flux entering the detection target surfaceWa. If a silicon photodiode, for instance, is provided at thelight-receiving surface under these circumstances, the angle ofincidence of the light flux entering the silicon photodiode increases,resulting in a high degree of surface reflection at the siliconphotodiode and an eclipse of the light flux which will induce a greatreduction in the quantity of light received.

[0054] Accordingly, in order to prevent a reduction in the lightreception quantity attributable to a large angle of incidence of thelight flux entering the light-receiving surface, the entry surface 11 aof the swing correction prism 11 constituting the deflection opticalsystem is provided at a plane that is conjugate with the detectiontarget surface Wa relative to the condenser optical system (8, 9) asshown in FIG. 1 in this embodiment. As a result, the light flux havingentered the entry surface 11 a of the swing correction prism 11 alongthe optical axis AX5 via the condenser optical system (8, 9) becomesdeflected at an angle of refraction which is equal to the apex angle(the angle formed by the entry surface and the exit surface) of theswing correction prism 11 and is emitted from the exit surface 11 balong an optical axis AX6. The exit surface 11 b is set perpendicular tothe optical axis X6.

[0055] The light having been emitted from the exit surface 11 b of theswing correction prism 11 along the optical axis AX6 then enters a relayoptical system (12, 13) constituted of a pair of lenses 12 and 13. Thelight having travelled through the relay optical system (12, 13) formsan image which is conjugate with the secondary image of the latticepattern 3 a formed on the entry surface 11 a of the swing correctionprism 11 and the openings Sa1˜Sa5 of the light-receiving slit S on thelight-receiving surface 14 a of a light-receiving unit 14. At thelight-receiving surface 14 a, five silicon photodiodes PD1˜PD5 areprovided to optically correspond to the openings Sa1˜Sa5 at thelight-receiving slit S respectively, as shown in FIG. 5. It is to benoted that instead of silicon photodiodes, a CCD (two-dimensional chargecoupled image-capturing element) or photomultiplier may be used.

[0056] As described above, in the embodiment in which the swingcorrection prism 11 is employed as the deflection optical system, theangle of incidence of the light flux entering the light-receivingsurface 14 a is reduced to a sufficient degree, thereby preventing areduction in the light reception quantity attributable to a large angleof incidence of the light flux at the light-receiving surface 14 a. Itis to be noted that it is desirable that the relay optical system (12,13) be constituted as a bilateral telecentric optical system asillustrated in FIG. 2. In addition, it is desirable that shine-proofingbe achieved for the entry surface 11 a of the swing correction prism 11and the light-receiving surface 14 a with respect to the relay opticalsystem (12, 13).

[0057] As explained earlier, the light-receiving slit S having the fiveopenings Sa1˜Sa5 is provided on the entry surface 11 a of the swingcorrection prism 11. Thus, the light constituting the secondary image ofthe lattice pattern 3 a formed on the entry surface 11 a is partiallyblocked via the light-receiving slit S. Namely, only the light flux fromthe secondary image of the lattice pattern 3 a formed over the areacorresponding to the openings Sa1˜Sa5 at the light-receiving slit S isallowed to reach the light-receiving surface 14 a via the swingcorrection prism 11 and the relay optical system (12, 13).

[0058] Thus, as shown in FIG. 5, images of the openings Sa1˜Sa5 at thelight-receiving slit S, i.e., slit images SL1˜SL5, are respectivelyformed on the silicon photodiodes PD1˜PD5 provided on thelight-receiving surface 14 a of the light-receiving unit 14. It isensured that the slit images SL1˜SL5 are formed inside the rectangularlight-receiving areas of the silicon photodiodes PD1˜PD5.

[0059] If the detection target surface Wa moves vertically in directionZ along the optical axis AX of the projection optical system PL, thesecondary image of the lattice pattern 3 a formed on the entry surface11 a of the swing correction prism 11 becomes laterally shifted alongthe direction of the pattern pitch in response to the vertical movementof the detection target surface Wa. In the embodiment, the extent of thelateral shift occurring in the secondary images of the lattice pattern 3a is detected and the surface position of the detection target surfaceWa along the optical axis AX of the projection optical system PL isdetected in correspondence to the detected lateral shift quantity, basedupon, for instance, the principle of photoelectric microscopy disclosedin Japanese Examined Patent Publication No. 42205/1981. The following isa brief explanation of a surface position detection achieved based uponthe principle of photoelectric microscopy.

[0060] As described earlier, FIG. 1 shows the oscillating mirror 10provided within the optical path of the condenser optical system (8, 9),which is driven to rotate forward/backward around the X axis by a mirrordrive unit 15. The mirror drive unit 15 oscillates the oscillatingmirror 10 over a specific cycle T along the direction indicated by thearrow in the figure, in response to a signal provided by an internaloscillator. As the oscillating mirror 10 oscillates, the secondary imageof the lattice pattern 3 a formed on the entry surface 11 a of the swingcorrection prism 11, too, oscillate along the direction of the patternpitch. At this time, the oscillation of the secondary image of thelattice pattern 3 a causes a change in the quantities of lighttransmitted through the openings Sa1˜Sa5 at the light-receiving slit S.The light transmitted through the light-receiving slit S travels throughthe relay optical system (12, 13) and reaches the silicon photodiodesPD1˜PD5 provided on the light-receiving surface 14 a of thelight-receiving unit 14.

[0061] The explanation is simplified by focusing on the light reachingone of the silicon photodiodes, i.e., the silicon photodiode PD1. Thelight having been transmitted through the opening Sa1 at thelight-receiving slit S forms the slit image SL1 on the siliconphotodiode PD1. The brightness of the slit image SL1 changes as theoscillating mirror 10 oscillates, In the embodiment, the width of theopening Sa1 (i.e., the measurement of the secondary image of the latticepattern 3 a along the direction of the pitch) is set equal to or smallerthan ½ of the pitch of the secondary image of the lattice pattern 3 aand, thus, the amplitude of the secondary image of the lattice pattern 3a is set equal to or smaller than ½ the pitch.

[0062] In addition, it is ensured that the center of the opening Sa1 isaligned with the center of the oscillation of the secondary image of thelattice pattern 3 a when the detection target surface Wa is aligned withthe image-forming plane of the projection optical system PL, Thus, whenthe secondary image of the lattice pattern 3 a oscillates as a result ofthe oscillation of the oscillating mirror 10, the light receptionquantity at the silicon photodiode PD1 changes. The silicon photodiodePD1 at the light-receiving unit 14 outputs a detection signalcorresponding to the change in the light intensity of the slit imageSL1, i.e., a detection signal reflecting the light modulation occurringin the slit image SL1, to a positional detection unit 16, Likewise, thesilicon photodiodes PD2˜PD5, too, output detection signals correspondingto the light modulation occurring in the slit images SL2˜SL5 to thepositional detection unit 16.

[0063] In addition, the mirror drive unit 15 also provides an AC signalat a phase matching that of the oscillation cycle T of the oscillatingmirror 10 to the positional detection unit 16. The positional detectionunit 16 performs synchronous rectification, i.e., synchronous phasedetection of the detection signals provided by the silicon photodiodesPD1˜PD5 at the light-receiving unit 14 in reference to the phase of theAC signal at the cycle T and outputs the resulting phase detectionoutput signals to a correction quantity calculation unit 17. The phasedetection output signals output from the positional detection unit 16are normally referred to as S curve signals each set to 0 level when thecorresponding detection area among the detection areas Da1˜Da5 on thedetection target surface Wa is set on the image-forming plane of theprojection optical system PL, i.e., when the detection signal isundergoing a change, with a cycle which is ½ the oscillation cycle T ofthe oscillating mirror 10.

[0064] The phase detection output signals indicate a positive level whenthe corresponding detection areas Da1˜Da5 at the detection targetsurface Wa are displaced farther upward relative to the image-formingplane of the projection optical system PL, whereas they indicate anegative level when the detection areas Da1˜Da5 at the detection targetsurface Wa are displaced further downward relative to the image-formingplane of the projection optical system PL. In other words, the phasedetection output signals each indicate an output value corresponding tothe change in the surface position of the detection target surface Wa.Accordingly, the correction quantity calculation unit 17 calculates theindividual positions of the detection areas Da1˜Da5 on the detectiontarget surface Wa along direction Z based upon the positive/negativelevels of the phase detection output signals that have been provided todetermine the average inclination of the detection target surface Wa andits position along direction Z.

[0065] Then, the correction quantity calculation unit 17 calculates atilt correction quantity and a direction Z correction quantity requiredto contain the detection target surface Wa within the range of the depthof focus of the projection optical system PL, and provides thecorrection quantities thus calculated to the holder drive unit 23. Theholder drive unit 23 implements drive control the holder supportingmechanism 22 based upon the tilt correction quantity and the direction Zcorrection quantity to level the wafer holder 21 and also move it alongdirection Z, and ultimately to level the wafer W and move the wafer Walong direction Z. Consequently, the wafer W is aligned relative to theprojection optical system PL with a high degree of accuracy so as tocontain the current exposure area at the exposure target surface Wawithin the range of the depth of focus of the projection optical systemPL. It is to be noted that specific details of the shine-proofingrequirements, the structures and effects of the deflecting prism 3 andthe swing correction prism 11 and the application of the principle ofphotoelectric microscopy are disclosed in Japanese Examined PatentPublication No. 97045/1994 filed by the applicant of the presentinvention.

[0066] Next, a detailed explanation is given on the structures assumedby and the effects achieved by the pentaprisms 6 and 7 constituting themeans for light flux deflection. As explained earlier, since thepentaprisms 6 and 7 adopt structures identical to each other, theyachieve similar advantages. Accordingly, the following explanationfocuses on the structure and the advantages of the pentaprism 6, forpurposes of simplification. The pentaprism 6 in FIG. 1 greatly deflectsa light flux traveling from above along direction −Z, so that deflectedlight advances along an almost horizontal direction to enter thedetection target surface Wa at a desired, relatively large angle ofincidence.

[0067]FIG. 6 illustrates the relationship between the angle ofintersection formed by the pair of reflection surfaces at the pentaprism6 in FIG. 1 and the angle of deflection achieved at the pentaprism 6. InFIG. 6, a light beam L1 having entered the pentaprism 6 along theoptical axis AX1 is sequentially reflected at the first reflectionsurface 6 b and the second reflection surface 6 c and then is emittedfrom the pentaprism 6 as a light beam L2 traveling along the opticalaxis AX2. In other words, the pentaprism 6 deflects the incident lightbeam L1 by an angle Φ. The relationship as expressed in the followingequation (1) is achieved between the angle of intersection Ψ formed bythe first reflection surface 6 b and the second reflection surface 6 cand the angle of deflection Φ formed by the incident light beam L1 andthe exiting light beam L2.

Φ+π=(π−2α)+(π−2β)  (1)

[0068] In the equation above, α represents the angle of incidence atwhich the light beam having entered the pentaprism 6 along the opticalaxis AX1 enters the first reflection surface 6 b and β represents theangle of incidence at which the light beam having entered the pentaprism6 along the optical axis AX1 enters the second reflection surface 6 c.These angles of incidence α and β achieve a relationship to the angle ofintersection Ψ as expressed in the following equation (2).

Ψ=α+β  (2)

[0069] Thus, equation (1) can be modified as expressed in the followingequation (3).

Φ+π=2π−2(α+β)=2π−2Φ  (3)

[0070] Based upon equation (3), the angle of deflection Φ is expressedas in the following equation (4).

Φ=π−2Ψ  (4)

[0071] Equation (4) indicates that the sole determining factor of theangle of deflection Φ of the pentaprism 6 is the angle of intersection Ψformed by the pair of reflection surfaces 6 b and 6 c, i.e., the angleof deflection Ψ is univocally determined by the angle of theintersection Ψ. As described earlier, the pair of reflection surfaces 6b and 6 c are constituted by forming a reflecting film on two sidesurfaces facing opposite each other at the pentagonal prism formed as anintegrated unit by using quartz class. As a result, the angle ofintersection Ψ formed by the pair of reflection surfaces essentiallydoes not change and ultimately, the angle of deflection Φ of thepentaprism 6 does not change either, due to vibration from the outside,temperature fluctuations and the like.

[0072] Consequently, since the relationship between the angularpositions (i.e., the angle of intersection Ψ) between the pair ofreflection surfaces 6 b and 6 c is sustained even when the pentaprism 6rotates by a slight degree around, for instance, the X axis (within theplane of incidence containing the optical axes AX1 and AX2) due todisplacement or distortion of the holding member attributable tovibration from the outside, temperature fluctuations and the like inthis embodiment, the angle of deflection Ψ of the pentaprism 6, too,remains constant, i.e., the direction along which the exiting light beamL2 travels remains unchanged and, thus, the angle of incidence of thelight flux entering the detection target surface Wa does not changeeither. While the spatial position of the exiting light beam changes incorrespondence to the distance between the pair of reflection surfaces 6b and 6 c, i.e., the exiting light beam L2 in FIG. 6 undergoes a lateralshift parallel to the optical axis AX2, the degree of this lateral shiftis insignificant enough to be disregarded in practical application,which means that the degree of positional shift occurring with regard tothe light flux entering the detection target surface Wa as a result ofthe lateral shift, too, is slight enough to be disregarded in practicalapplication.

[0073] In contrast, if a regular reflecting mirror (a mirror having asingle reflection surface) is provided in place of the pentaprism 6 asin the prior art, a slight rotation of the reflection surface of thereflecting mirror around, for instance, the X axis, caused bydisplacement or deformation of the holding member attributable tovibration from the outside, temperature fluctuations and the like willresult in the angle of deflection of the reflecting mirror changing bytwice the tilt angle (the angle of the slight rotation) and,consequently, the position at which the light flux enters the detectiontarget surface changes together with the angle of incidence at thedetection target surface. Under these circumstances, the degree by whichthe entry position changes is almost in proportion to the change in theangle of incidence and the distance between the detection target surfaceand the reflection surface of the reflecting mirror.

[0074] The change in the angle of incidence occurring at this timerelates to a change in the detection conversion coefficient used whendetecting the surface position of the detection target surface and thechange in the entry position results in a change in the position atwhich the pattern image is formed, and thus, either of these changesinduces a detection error in detecting the position of the detectiontarget surface. In other words, even when the surface position of thedetection target surface does not change at all in reality, the positionat which the pattern image is formed on the light-receiving slit changesas a result of a change in the angle of incidence or a change in theentry position attributable to the change in the angle of deflection ofthe reflecting mirror. Consequently, an erroneous detection is performedto indicate that a change has occurred in the surface position of thedetection target surface which actually has not changed.

[0075] As explained above, even when the pentaprism 6 becomes tilted bya slight degree within the plane of incidence as a result ofdisplacement or deformation of the holding member attributable toexternal vibration, temperature fluctuations and the like, the angle ofdeflection of the pentaprism 6 remains constant and, therefore, theangle of incidence at the detection target surface remains unchanged inthe embodiment. Thus, unlike in the prior art in which a reflectingmirror that reflects light at a single surface is employed, a detectionerror attributable to external vibration, temperature fluctuations andthe like can be successfully eliminated by preventing a change in theangle of incidence and a change in the entry position which is affectedby the distance between the detection target surface and the reflectingmirror.

[0076] Similar advantages are achieved at the pentaprism 7 to thoseachieved at the pentaprism 6. Namely, even when the pentaprism 7 becomestilted by a slight degree within the plane of incidence as a result ofdisplacement or deformation of the holding member attributable tovibration from the outside, temperature fluctuations and the like, theangle of deflection of the pentaprism 7 does not change and therefore,the angle of incidence at the light-receiving slit S and the angle ofincidence at the light-receiving surface 14 a do not change either.Thus, unlike the prior art in which a reflecting mirror that reflectslight at a single surface is employed, a detection error attributable tovibration from the outside, temperature fluctuations and the like can besuccessfully eliminated by preventing a change in the angle of incidenceat the light-receiving slit S and a change in the entry position whichis affected by the distance between the reflecting mirror and thelight-receiving slit S.

[0077] In addition, in the embodiment, the pentaprisms 6 and 7 arerespectively provided in the optical path between the projection opticalsystem (4, 5) and the detection target surface Wa and the optical pathbetween the condenser optical system (8, 9) and the detection targetsurface Wa to greatly deflect the optical path of the light fluxentering the detection target surface Wa and the optical path of a lightflux having been reflected at the detection target surface Wa throughthe pentaprisms 6 and 7, so as to allow the projection optical system(4, 5) and the condenser optical system (8, 9) to be set over sufficientdistances from the detection target surface Wa. As a result, thestructures and the positions of the projection optical system (4, 5) andthe condenser optical system (8, 9) are essentially free of anyrestrictions that may otherwise be imposed by the proximity of thedetection target surface Wa.

[0078] As described above, the surface position detection device in theembodiment, which essentially remains free of any restrictions imposedby the proximity of the detection target surface Wa with regard to thestructures and the positions of the optical systems successfullyprevents deterioration in the detection accuracy attributable tovibration from the outside, temperature fluctuations and the like. As aresult, a projection exposure apparatus provided with the surfaceposition detection device in the embodiment, which remains essentiallyunaffected by vibration of the apparatus, ambient air temperaturefluctuations and the like, is capable of achieving highly accuratealignment of the mask pattern surface and the exposure target surface ofthe photosensitive substrate relative to the projection optical systemand, thus, is capable of manufacturing appropriate micro devices.

[0079] However since deflected light fluxes are shifted slightly (thepositions at which light fluxes exit the pentaprisms change) as a resultof slight inclinations of the pentaprisms 6 and 7 in this embodiment, itis desirable to form the pentaprisms in a size which is small aspossible (to minimize the lengths of the optical paths within thepentaprisms). Accordingly, since the required angle of intersection Ψ ofthe pair of reflection surfaces is defined in conformance to therequired angle of deflection Φ through equation (4) explained earlier,each pentaprism is formed in a compact size in correspondence to therequired angle of intersection Ψ and the pair of effective reflectionareas that should be assured.

[0080] It is to be noted that if the angle of intersection of the pairof reflection surfaces is changed due to thermal expansion of thepentaprism itself the angle of deflection (and ultimately, the angles ofincidence and the entry positions at the detection target surface andthe light-receiving surface) changes to induce a detection error.Accordingly, it is desirable to constitute the pentaprism with anoptical material that does not readily expand when heated such as quartzglass. More specifically, it is desirable to constitute the pentaprismwith an optical material having a coefficient of thermal expansion equalto or lower than 1 ppm/K, and the coefficient of thermal expansion ofquartz glass is approximately 0.5 ppm/K satisfying this requirement.

[0081] Examples of such glass materials that do not expand readily whenheated include titanium silicate glass (e.g., ULE (trademark) availablefrom Corning Incorporated in New York State, USA), ZeroDua (trademark)also available from Corning Incorporated, CliarceramZ (trademark)available from Ohara Corp. in Sagamihara, Kanagawa Prefecture and thelike. The coefficient of thermal expansion achieved by ULE is +0.05ppm/K, the coefficient of thermal expansion achieved by ZeroDu a is−0.03 ppm/K and the coefficient of thermal expansion achieved byCliarceramZ is 0.08 ppm/K. It is to be noted that quartz glass is themost desirable glass material that does not expand readily when heatedsince it achieves an optimal transmittance.

[0082] In addition, it is desirable to constitute the pentaprisms with alow-dispersion optical material such as quartz glass in order to reducethe occurrence of chromatic aberration inside the prisms. In morespecific terms, the optical material used to constitute the pentaprismsshould have an Abbe number of 65 or higher and quartz glass has an Abbenumber of approximately 68, satisfying the requirement.

[0083] As mentioned earlier, the angle of incidence at which the lightflux enters the detection target surface Wa should be set as large aspossible (set as close to 90° as possible) to improve the accuracy withwhich the surface position of the detection target surface Wa isdetected. Since the light flux entering along direction −Z is deflectedby the deflection angle Ψ to allow it to enter the detection targetsurface Wa parallel to the XY plane in the embodiment, the relationshipexpressed as Φ=π−θ is achieved between the angle of incidence θ and theangle of reflection θ at the detection target surface Wa and the angleof deflection Φ.

[0084] Accordingly, if the desired angle of incidence θ and angle ofreflection θ are set at, for instance, 80°≦θ<90°, angle of deflection Φat the pentaprism is within a range of 100°≧θ>90°, which it sets theangle of intersection Ψ of the pair of reflection surfaces at thepentaprism within a range of 40°≦Ψ<45° in conformance to therelationship expressed in equation (4). In other words, by using apentaprism achieving an angle of intersection Ψ within a range of40°≧y>45°, the angle of incidence of the light flux entering thedetection target surface Wa can be set at a desirable value, and thenthe projection optical system (4, 5) and the condenser optical system(8, 9) can be positioned along the vertical direction as is theprojection optical system PL.

[0085]FIG. 7 schematically illustrates the structure of an essentialportion of a projection exposure apparatus provided with a surfaceposition detection device achieved as a variation of the embodimentshown in FIG. 1. The variation in FIG. 7 assumes a structure similar tothat adopted in the embodiment shown in FIG. 14 However, the variationin FIG. 7 differs from the embodiment shown in FIG. 1 in that rhombicprisms 31 and 32 are respectively provided in the optical, path betweenthe pentaprism 6 and the detection target surface Wa and the opticalpath between the pentaprism 7 and the detection target surface Wa.Accordingly, the same reference numbers as those in FIG. 1 are assignedto elements achieving functions identical to the components in theembodiment shown in FIG. 1. The following is an explanation of thevariation shown in FIG. 7 by focusing on the differences from theembodiment in FIG. 1.

[0086] In the variation in FIG. 7, a light flux having exited thepentaprism 6 along the optical as AX2 enters the rhombic prism 31. Therhombic prism 31 is a quadrangular prism having a rhombic cross sectionand its longer axis extends along direction X as does the longer axis ofthe pentaprism 6. At the rhombic prism 31, light having been transmittedthrough a first transmission surface 31 a perpendicular to the opticalaxis AX2 is sequentially reflected at a pair of reflection surfaces 31 band 31 c which are parallel to each other, is then transmitted through asecond transmission surface 31 d parallel to the first transmissionsurface 31 a and exits the rhombic prism 31 along an optical axis AX21parallel to the optical axis AX2. The light flux having exited therhombic prism 31 along the optical axis AX21 then enters the detectiontarget surface Wa.

[0087] A light flux having been reflected at the detection targetsurface Wa along an optical axis AX31 that is symmetrical to the opticalaxis AX21 relative to the optical axis AX of the projection opticalsystem PL, on the other hand, enters the rhombic prism 32. The rhombicprism 32, which is similar to the rhombic prism 31, is a quadrangularprism having its longer axis extending along direction X and having arhombic cross section. As a result, at the rhombic prism 32, lighthaving been transmitted through a first transmission surface 32 aperpendicular to the optical axis AX31 is sequentially reflected at apair of reflection surfaces 32 b and 32 c parallel to each other, istransmitted through a second transmission surface 32 d parallel to thefirst transmission surface 32 a and exits the rhombic prism 32 along anoptical axis AX3 parallel to the optical axis AX31.

[0088] As explained above, in the variation shown in FIG. 7, which isprovided with the rhombic prisms 31 and 32 respectively in the opticalpath between the pentaprism 6 and the detection target surface Wa andthe optical path between the pentaprism 7 and the detection targetsurface Wa, the optical path of the light flux entering the detectiontarget surface Wa and the optical path of the light flux having beenreflected at the detection target surface Wa are caused to undergoparallel movement by the rhombic prisms 31 and 32 respectively. As aresult, the pair of optical prisms 6 and 7 can be set over distancesfrom the detection target surface Wa to essentially free the pair ofpentaprisms and their holding members from any structural and positionalrestrictions imposed by the proximity of the detection target surfaceWa.

[0089] While the means for light flux deflection are constituted ofpentaprisms in the embodiment shown in FIG. 1, the means for light fluxdeflection may be instead constituted by using a pair of reflectingmirrors that are not parallel to each other and holding members thatinterlock and hold the pair of reflecting mirrors by intermitting withthem. FIG. 8 schematically illustrates a structure that may be adoptedin such a variation of the means for light flux deflection and FIG. 9schematically illustrates the structure of the holding members in FIG.8.

[0090] In the variation shown in FIG. 8, a first reflecting mirror 41and a second reflecting mirror 42 respectively having reflectionsurfaces corresponding to the first reflection surface and the secondreflection surface of the pentaprism 6 in FIG. 1 are interfitted withand held by a first mirror holding member 43 and a second mirror holdingmember 44 respectively. The first mirror holding member 43 and thesecond mirror holding member 44 are either formed as an integrated partof a base 45 or are mounted at the base 45. Thus, the base 45 holds thefirst reflecting mirror 41 and the second reflecting mirror 42 via thefirst mirror holding member 43 and the second mirror holding member 44so as to sustain the angle of intersection Ψ formed by the reflectionsurface of the first reflecting mirror 41 and the reflection surface ofthe second reflecting mirror 42 unchanged.

[0091] In FIG. 9, a mirror holding member 70 (which corresponds to thefirst mirror holding member 43 and the second mirror holding member 44in FIG. 8) holds a reflecting mirror 51, which corresponds to the firstreflecting mirror 41 and the second reflecting mirror 42 in FIG. 8achieving rotation symmetry (having a disk shape with a constantthickness and a constant external diameter, more specifically) and isprovided with an optical material holding metal hardware piece 81,spacers 82 and a retainer ring 83.

[0092] The optical material holding metal hardware piece 81, assumes astaged shape on its internal circumferential side and assumes a roughlycylindrical shape with a constant diameter on its externalcircumferential side. Namely, at on internal circumference, a firstinternal diameter portion 85 is formed on one side along the directionin which the axis extends arid a second internal diameter portion 86 isformed on the other side along the axial direction. The first internaldiameter portion 85 has a diameter smaller than that of the secondinternal diameter portion 86 and, as a result, a stage 87 is formedperpendicular to the direction in which the axis extends.

[0093] Three trapezoidal support portions 89 are formed so as to projectoutward toward the center at the end of the first internal diameterportion 85 on the side opposite from the side where the second internaldiameter portion 86 is formed. These support portions 89 are formed inidentical shapes, and are provided over equal intervals along thecircumferential direction at the optical material holding metal hardwarepiece 81. The support portions 89 are each provided with a trapezoidalcontact surface 89 a perpendicular to the direction along which the axisextends, toward the second internal diameter portion 86 along thedirection of the axis of the optical material holding metal hardwarepiece 81. These contact surfaces 89 a, which have identical shapes, areset within a single plane perpendicular to the direction of the axis ofthe optical material holding metal hardware piece 81.

[0094] In addition, a female screw 91 is formed at the end of the secondinternal diameter portion 86 on the side opposite from the side wherethe first internal diameter portion 85 is provided. At the stagedportion 87, insertion holes (only one is shown) 92 each paired andaligned with the support portion 89 along the radial direction areformed. The reflecting mirror 51 is inserted through the second internaldiameter portion 85 to the optical material holding metal hardware piece81 so that a peripheral portion 62 at the other surface 51 a of thereflecting mirror 51 is mounted at the contact surfaces 89 a of thesupport portions 89.

[0095] The spacers 82 are each mounted at the corresponding insertionhole 92, and are each provided with a pair of parallel shafts 93inserted at the insertion hole 92 and a mounting plate 94 extending fromthe shafts 93 along a direction perpendicular to the axial direction. Byinserting the individual spacers 82 at the insertion holes 92, a contactsurface 94 a of the mounting plate 94 of each spacer 82 is placed incontact with the peripheral portion 62 at a surface 51 b of thereflecting mirror 51.

[0096] The shape of the contact surfaces 94 a of the mounting plates 94placed in contact with the surface 51 b of the reflecting mirror 51matches the shape of the contact surfaces 89 a of the support portions89 placed in contact with the other surface 51 a of the reflectingmirror 51. As a result, these contact surfaces 94 a and 89 a have areasequal to each other. In addition, the corresponding contact surfaces 94a and 89 a are set at positions facing opposite each other (at matchingpositions along the direction of the circumference of the opticalmaterial holding metal hardware piece 81).

[0097] The retainer ring 83 assumes a staged shape on its externalcircumferential side and a roughly ring shape with a constant diameteron its internal circumferential side. Namely, on its externalcircumferential side, a first external diameter portion 96 is formed onone side along the axial direction and a second external diameterportion 97 is formed on the other side along the axial direction. Thefirst external diameter portion 96 has a diameter larger than thediameter of the second external diameter portion 97, with a male screw98 formed at the first external diameter portion 96. The retainer ring83 is mounted at the metal hardware piece 81 by interlocking the malescrew 98 with the female screw 91 of the optical material holding metalhardware piece 81 having the reflecting mirror 51 inserted at the firstinternal diameter portion 85 and all the spacers 82 mounted therein.When the retainer ring 83 is screwed in at the optical material holdingmetal hardware piece 81, the reflecting mirror 51 is clamped by thetrapezoidal contact surfaces 89 a of the support portions 89 and thetrapezoidal contact surfaces 94 a of the mounting plates 94 from the twosides along the axial direction.

[0098] By utilizing the mirror holding member 70, it is possible to holdthe reflecting mirror 51 without having to use an adhesive. As a result,the reflection surface of the reflecting mirror 51 is effectivelyprevented from becoming tilted within the plane of incidence as a resultof deformation or the like of the adhesive attributable to, forinstance, ambient air temperature fluctuations. It is to be noted thatit is desirable to constitute the pair of mirror holding members 43 and44 and the base 45 with a material having a coefficient of thermalexpansion equal to or lower than 1 ppm/K, which does not expand readilywhen heated, to sustain the angle of intersection of the pair ofreflecting mirrors 41 and 42 unchanged. More specifically, these membersmay be formed by using a ceramics, glass, an alloy or the like that doesnot expand readily in heat.

[0099] It is to be noted that while the pentaprisms 6 and 7 are providedrespectively in the optical path between the projection optical system(4, 5) and the detection target surface Wa and the optical path betweenthe condenser optical system (8, 9) and the detection target surface Wain the embodiment and its variation described above, the advantages ofthe present invention may be achieved by providing a pentaprism in, atleast, either of the optical paths.

[0100] In addition, while an explanation is given above in reference tothe embodiment and the variation on an example in which a projectionexposure apparatus is provided with a single surface position detectiondevice, the present invention is not restricted by these details, and aplurality of surface position detection devices may be provided asnecessary to perform detection over individual areas achieved bypartitioning the detection field. In such a case, the individual devicescm be calibrated based upon the results of detection obtained at acommon field contained in both the detection field in which thedetection is performed by a first surface position detection device andthe detection field in which the detection is performed by a secondsurface position detection device,

[0101] While a means for light flux deflection is constituted by using apentagonal prism having a pair of reflection surfaces or a mirrorassembly having a pair of reflecting mirrors in the embodiment and thevariations explained above, the present invention is not limited tothese particulars, and a means for light flux deflection may beconstituted by using a prism having an even number of reflectionsurfaces or a mirror assembly having an even number of reflectionsurfaces.

[0102] Furthermore, while the present invention is adopted in detectionof the surface position of a photosensitive substrate in a projectionexposure apparatus in the embodiment and the variations, it may also beadopted in detection of the surface position of a mask in a projectionexposure apparatus.

[0103] Also, while the present invention is adopted in detection of thesurface position of a photosensitive substrate in a projection exposureapparatus in the embodiment and the variations, it may also be adoptedin detection of the surface position of an ordinary detection targetsurface, instead.

[0104] As explained above, in the surface position detection deviceaccording to the present invention, which is provided with means forlight flux deflection each constituted of, for instance, a pentaprism,in the optical path between the projection optical system and thedetection target surface and the optical path between the condenseroptical system and the detection target surface to greatly deflect theoptical path of the light flux entering the detection target surface andthe optical path of a light flux having been reflected at the detectiontarget surface, the projection optical system and the condenser opticalsystem are allowed to be set over distances from the detection targetsurface to free these optical systems from any structural and positionalrestrictions imposed by the proximity of the detection target surface.

[0105] In addition, even when the pentaprism becomes tilted by a slightdegree within, for instance, the plane of incidence as a result ofdisplacement or deformation of the holding member attributable tovibration from the outside, temperature fluctuations and the like, theangle of deflection achieved at the pentaprism remains unchanged, i.e.,the exiting light flux advances along a constant direction and,ultimately, that angle of incidence of the light flux entering thedetection target surface or the light-receiving surface, too, remainsunchanged. As a result, since hardly any changes occur in the angles ofincidence at the detection target surface and the light-receivingsurface and the entry positions at the detection target surface and thelight-receiving surface, occurrence of a detection error attributable toexternal vibration, temperature fluctuations and the like can besuccessfully prevented.

[0106] Moreover, by adopting the surface position detection deviceaccording to the present invention in detection of the surface positionof a photosensitive substrate relative to the projection optical systemin a projection exposure apparatus, highly accurate alignment of themask pattern surface and the exposure target surface of thephotosensitive substrate relative to the projection optical system isachieved essentially without being affected by vibration of theprojection exposure apparatus, ambient air temperature fluctuations orthe like and, as a result, appropriate micro devices can bemanufactured.

What is claimed is;
 1. A surface position detection device for detectinga surface position of a detection target surface, comprising; aprojection system that projects a light flux from a diagonal directiononto the detection target surface; a light-receiving system thatreceives a light flux having been reflected at the detection targetsurface; and a means for light flux deflection provided, at least,either in an optical path of said projection system or in an opticalpath of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux, wherein: the surfaceposition of the detection target surface is detected based upon anoutput from said light-receiving system.
 2. A surface position detectiondevice for detecting a surface position of a detection target surface,comprising; a projection system that projects a light flux from adiagonal direction onto the detection target surface; a light-receivingsystem that receives a light flux having been reflected at the detectiontarget surface; and a means for light flux deflection provided, atleast, either in an optical path of said projection system or in anoptical path of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux, which includes a prismhaving a pair of reflection surfaces that are not parallel to eachother, wherein: the surface position of the detection target surface isdetected based upon an output from said light-receiving system.
 3. Asurface position detection device according to claim 2, wherein: saidprism is constituted of an optical material having a coefficient ofthermal expansion equal to or lower than 1 ppm/K, which does not expandreadily in heat.
 4. A surface position detection device for detecting asurface position of a detection target surface, comprising; a projectionsystem that projects a light flux from a diagonal direction onto thedetection target surface; a light-receiving system that receives a lightflux having been reflected at the detection target surface; and a meansfor light flux deflection provided, at least, either in an optical pathof said projection system or in an optical path of said light-receivingsystem and having an even number of reflection surfaces to allow anincident light flux to exit at an angle that is not parallel to theincident light flux, which includes a prism having a pair of reflectionsurfaces that are not parallel to each other and constituted of alow-dispersion optical material with an Abbe number of 65 or higher,wherein: the surface position of the detection target surface isdetected based upon an output from said light-receiving system.
 5. Asurface position detection device according to claim 4, wherein: saidprism is constituted of an optical material having a coefficient ofthermal expansion equal to or lower than 1 ppm/K, which does not expandreadily in heat.
 6. A surface position detection device for detecting asurface position of a detection target surface, comprising; a projectionsystem that projects a light flux from a diagonal direction onto thedetection target surface; a light-receiving system that receives a lightflux having been reflected at the detection target surface; and a meansfor light flux deflection provided, at least, either in an optical pathof said projection system or in an optical path of said light-receivingsystem and having an even number of reflection surfaces to allow anincident light flux to exit at an angle that is not parallel to theincident light flux, which includes a prism having a pair of reflectionsurfaces that are not parallel to each other, wherein: said prismincludes a first transmission surface through which the incident lightflux is transmitted, a first reflection surface at which the light fluxhaving been transmitted through said first transmission surface andpropagated through the inside of said prism is reflected, a secondreflection surface at which the light flux having been reflected at saidfirst reflection surface and propagated through the inside of said primis reflected along an optical path intersecting the optical path of thelight flux having been transmitted through said first transmissionsurface and a second transmission surface through which the light fluxhaving been reflected at said second reflection surface and propagatedthrough the inside of said prism is transmitted; and the surfaceposition of the detection target surface is detected based upon anoutput from said light-receiving system.
 7. A surface position detectiondevice according to claim 6, wherein: said prism is constituted of anoptical material having a coefficient of thermal expansion equal to orlower than 1 ppm/K, which does not expand readily in heat.
 8. A surfaceposition detection device for detecting a surface position of adetection target surface, comprising; a projection system that projectsa light flux from a diagonal direction onto the detection targetsurface; a light-receiving system that receives a light flux having beenreflected at the detection target surface; and a means for light fluxdeflection provided, at least, either in an optical path of saidprojection system or in an optical path of said light-receiving systemand having an even number of reflection surfaces to allow an incidentlight flux to exit at an angle that is not parallel to the incidentlight flux, which includes a prism having a pair of reflection surfacesthat are not parallel to each other, wherein: said prism includes afirst transmission surface through which the incident light flux istransmitted, a first reflection surface at which the light flux havingbeen transmitted through said first transmission surface and propagatedthrough the inside of said prism is reflected, a second reflectionsurface at which the light flux having been reflected at said firstreflection surface and propagated through the inside of said prim isreflected along an optical path intersecting the optical path of thelight flux having been transmitted through said first transmissionsurface and a second transmission surface through which the light fluxhaving been reflected at said second reflection surface and propagatedthrough the inside of said prism is transmitted and is constituted of alow-dispersion optical material with an Abbe number of 65 or higher; andthe surface position of the detection target surface is detected basedupon an output from said light-receiving system.
 9. A surface positiondetection device according to claim 8, wherein: said prism isconstituted of an optical material having a coefficient of thermalexpansion equal to or lower than 1 ppm/K, which does not expand readilyin heat.
 10. A surface position detection device for detecting a surfaceposition of a detection target surface, comprising; a projection systemthat projects a light flux from a diagonal direction onto the detectiontarget surface; a light-receiving system that receives a light fluxhaving been reflected at the detection target surface; and a means forlight flux deflection provided, at least, either in an optical path ofsaid projection system or in an optical path of said light-receivingsystem and having an even number of reflection surfaces to allow anincident light flux to exit at an angle that is not parallel to theincident light flux, which includes a prism having a pair of reflectionsurfaces that are not parallel to each other, wherein: said prismincludes a first transmission surface through which the incident lightflux is transmitted, a first reflection surface at which the light fluxhaving been transmitted through said first transmission surface andpropagated through the inside of said prism is reflected, a secondreflection surface at which the light flux having been reflected at saidfirst reflection surface and propagated through the inside of said primis reflected along an optical path intersecting the optical path of thelight flux having been transmitted through said first transmissionsurface and a second transmission surface through which the light fluxhaving been reflected at said second reflection surface and propagatedthrough the inside of sad prism is transmitted, with the angle formed bysaid first reflection surface and said second reflection surface setwithin a range of 40° or more and less than 45°; and the surfaceposition of the detection target surface is detected based upon anoutput from said light-receiving system.
 11. A surface positiondetection device according to claim 10, wherein: said prism isconstituted of an optical material having a coefficient of thermalexpansion equal to or lower than 1 ppm/K, which does not expand readilyin heat.
 12. A surface position detection device for detecting a surfaceposition of a detection target surface, comprising; a projection systemthat projects a light flux from a diagonal direction onto the detectiontarget surface; a light-receiving system that receives a light fluxhaving been reflected at the detection target surface; and a means forlight flux deflection provided, at least, either in an optical path ofsaid projection system or in an optical path of said light-receivingsystem and having an even number of reflection surfaces to allow anincident light flux to exit at an angle that is not parallel to theincident light flux, which includes a prism having a pair of reflectionsurfaces that are not parallel to each other, wherein: said prismincludes a first transmission surface through which the incident lightflux is transmitted, a first reflection surface at which the light fluxhaving been transmitted through said first transmission surface andpropagated through the inside of said prism is reflected, a secondreflection surface at which the light flux having been reflected at saidfirst reflection surface and propagated through the inside of said primis reflected along an optical path intersecting the optical path of thelight flux having been transmitted through said first transmissionsurface and a second transmission surface through which the light fluxhaving been reflected at said second reflection surface and propagatedthrough the inside of said prism is transmitted, with the angle formedby said first reflection surface and said second reflection surface setwithin a range of 40° or more and less than 45° and is constituted of alow-dispersion optical material with an Abbe number of 65 or higher; andthe surface position of the detection target surface is detected basedupon an output from said light-receiving system.
 13. A surface positiondetection device according to clam 12, wherein: said prism isconstituted of an optical material having a coefficient of thermalexpansion equal to or lower than 1 ppm/K, which does not expand readilyin heat.
 14. A surface position detection device for detecting a surfaceposition of a detection target surface, comprising; a projection systemthat projects a light flux from a diagonal direction onto the detectiontarget surface and includes a projection optical system provided to forma prier image of a specific pattern onto the detection target surface; alight-receiving system that receives a light flux having been reflectedat the detection target surface and includes a condenser optical systemprovided to form a secondary image of the specific pattern by condensingthe light flux having been reflected at the detection target surface anda detection unit provided to detect the secondary image of the specificpattern formed via said condenser optical system; and a means for lightflux deflection provided, at least, either in an optical path of saidprojection system or in an optical path of said light-receiving systemand having an even number of reflection surfaces to allow an incidentlight flux to exit at an angle that is not parallel to the incidentlight flux, wherein: the surface position of the detection targetsurface is detected based upon an output from said detection unit.
 15. Asurface position detection device for detecting a surface position of adetection target surface, comprising; a projection system that projectsa light flux from a diagonal direction onto the detection target surfaceand includes a projection optical system provided to form a primaryimage of a specific pattern onto the detection target surface; alight-receiving system that receives a light flux having been reflectedat the detection target surface and includes a condenser optical systemprovided to form a secondary image of the specific pattern by condensingthe light flux having been reflected at the detection target surface anda detection unit provided to detect the secondary image of the specificpattern formed via said condenser optical system; and a means for lightflux deflection provided, at least, either in an optical path of saidprojection system or in an optical path of said light-receiving systemand having an even number of reflection surfaces to allow an incidentlight flux to exit at an angle that is not parallel to the incidentlight flux, which includes a prism having a pair of reflection surfacesthat are not parallel to each other, wherein: the surface position ofthe detection target surface is detected based upon an output from saiddetection unit.
 16. A surface position detection device according toclaim 15, wherein: said prism is constituted of an optical materialhaving a coefficient of thermal expansion equal to or lower than 1ppm/K, which does not expand readily in heat.
 17. A surface positiondetection device for detecting a surface position of a detection targetsurface, comprising; a projection system that projects a light flux froma diagonal direction onto the detection target surface and includes aprojection optical system provided to form a primary image of a specificpattern onto the detection target surface; a light-receiving system thatreceives a light flux having been reflected at the detection targetsurface and includes a condenser optical system provided to form asecondary image of the specific pattern by condensing the light fluxhaving been reflected at the detection target surface and a detectionunit provided to detect the secondary image of the specific patternformed via said condenser optical system; and a means for light fluxdeflection provided, at least, either in an optical path of saidprojection system or in an optical path of said light-receiving systemand having an even number of reflection surfaces to allow an incidentlight flux to exit at an angle that is not parallel to the incidentlight flux, which includes a prism having a pair of reflection surfacesthat are not parallel to each other and constituted of a low-dispersionoptical material with an Abbe number of 65 or higher, wherein: thesurface position of the detection target surface is detected based uponan output from said detection unit.
 18. A surface position detectiondevice according to claim 17, wherein: said prism is constituted of anoptical material having a coefficient of thermal expansion equal to orlower than 1 ppm/K, which does not expand readily in heat.
 19. A surfaceposition detection device for detecting a surface position of adetection target surface, comprising; a projection system that projectsa light flux from a diagonal direction onto the detection target surfaceand includes a projection optical system provided to form a primaryimage of a specific pattern onto the detection target surface; alight-receiving system that receives a light flux having been reflectedat the detection target surface and includes a condenser optical systemprovided to form a secondary image of the specific pattern by condensingthe light flux having been reflected at the detection target surface anda detection unit provided to detect the secondary image of the specificpattern formed via said condenser optical system; and a means for lightflux deflection provided, at least, either in an optical path of sadprojection system or in an optical path of said light-receiving systemand having an even number of reflection surfaces to allow an incidentlight flux to exit at an angle that is not parallel to the incidentlight flux, which includes a prism having a pair of reflection surfacesthat are not parallel to each other, wherein: said prism includes afirst transmission surface through which the incident light flux istransmitted, a first reflection surface at which the light flux havingbeen transmitted through said first transmission surface and propagatedthrough the inside of said prism is reflected, a second reflectionsurface at which the light flux having been reflected at said firstreflection surface and propagated through the inside of said prim isreflected along an optical path intersecting the optical path of thelight flux having been transmitted through said first transmissionsurface and a second transmission surface through which the light fluxhaving been reflected at said second reflection surface and propagatedthrough the inside of said prism is transmitted; and the surfaceposition of the detection target surface is detected based upon anoutput from said detection unit.
 20. A surface position detection deviceaccording to claim 19, wherein: said prism is constituted of an opticalmaterial having a coefficient of thermal expansion equal to or lowerthan 1 ppm/K, which does not expand readily in heat.
 21. A surfaceposition detection device for detecting a surface position of adetection target surface, comprising; a projection system that projectsa light flux from a diagonal direction onto the detection target surfaceand includes a projection optical system provided to form a primaryimage of a specific pattern onto the detection target surface; alight-receiving system that receives a light flux having been reflectedat the detection target surface and includes a condenser optical systemprovided to form a secondary image of the specific pattern by condensingthe light flux having been reflected at the detection target surface anda detection unit provided to detect the secondary image of the specificpattern formed via said condenser optical system; and a means for lightflux deflection provided, at least, either in an optical path of saidprojection system or in an optical path of said light-receiving systemand having an even number of reflection surfaces to allow an incidentlight flux to exit at an angle that is not parallel to the incidentlight flux, which includes a prism having a pair of reflection surfacesthat are not parallel to each other, wherein: said prism includes afirst transmission surface through which the incident light flux istransmitted, a first reflection surface at which the light flux havingbeen transmitted through said first transmission surface and propagatedthrough the inside of said prism is reflected, a second reflectionsurface at which the light flux having been reflected at said firstreflection surface and propagated through the inside of said prim isreflected along an optical path intersecting the optical path of thelight flux having been transmitted through said first transmissionsurface and a second transmission surface through which the light fluxhaving been reflected at said second reflection surface and propagatedthrough the inside of said prism is transmitted and is constituted of alow-dispersion optical material with an Abbe number of 65 or higher; andthe surface position of the detection target surface is detected basedupon an output from said detection unit.
 22. A surface positiondetection device according to claim 21, wherein: said prism isconstituted of an optical material having a coefficient of thermalexpansion equal to or lower than 1 ppm/K, which does not expand readilyin heat.
 23. A surface position detection device for detecting a surfaceposition of a detection target surface, comprising; a projection systemthat projects a light flux from a diagonal direction onto the detectiontarget surface and includes a projection optical system provided to forma primary image of a specific pattern onto the detection target surface;a light-receiving system that receives a light flux having beenreflected at the detection target surface and includes a condenseroptical system provided to form a secondary image of the specificpattern by condensing the light flux having been reflected at thedetection target surface and a detection unit provided to detect thesecondary image of the specific pattern formed via said condenseroptical system; and a means for light flux deflection provided, atleast, either in an optical path of said projection system or in anoptical path of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux, which includes a prismhaving a pair of reflection surfaces that are not parallel to eachother, wherein: said prism includes a first transmission surface throughwhich the incident light flux is transmitted, a first reflection surfaceat which the light flux having been transmitted through said firsttransmission surface and propagated through the inside of said prism isreflected, a second reflection surface at which the light flux havingbeen reflected at said first reflection surface and propagated throughthe inside of said prim is reflected along an optical path intersectingthe optical, path of the light flux having been transmitted through saidfirst transmission surface and a second transmission surface throughwhich the light flux having been reflected at said second reflectionsurface and propagated through the inside of said prism is transmitted,with the angle formed by said first reflection surface and said secondreflection surface set within a range of 40° or more and less than 45°;and the surface position of the detection target surface is detectedbased upon an output from said detection unit.
 24. A surface positiondetection device according to claim 23, wherein: said prism isconstituted of an optical material having a coefficient of thermalexpansion equal to or lower than 1 ppm/K, which does not expand readilyin heat.
 25. A surface position detection device for detecting a surfaceposition of a detection target surface, comprising; a projection systemthat projects a light flux from a diagonal direction onto the detectiontarget surface and includes a projection optical system provided to forma primary image of a specific pattern onto the detection target surface;a light-receiving system that receives a light flux having beenreflected at the detection target surface and includes a condenseroptical system provided to form a secondary image of the specificpattern by condensing the light flux having been reflected at thedetection target surface and a detection unit provided to detect thesecondary image of the specific pattern formed via said condenseroptical system; and a means for light flux deflection provided, atleast, either in an optical path of said projection system or in anoptical path of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux, which includes a prismhaving a pair of reflection surfaces that are not parallel to eachother, wherein: said prism includes a first transmission surface throughwhich the incident light flux is transmitted, a first reflection surfaceat which the light flux having been transmitted through said firsttransmission surface and propagated through the inside of said prism isreflected, a second reflection surface at which the light flux havingbeen reflected at said first reflection surface and propagated throughthe inside of said prim is reflected along an optical path intersectingthe optical path of the light flux having been transmitted through saidfirst transmission surface and a second transmission surface throughwhich the light flux having been reflected at said second reflectionsurface and propagated through the inside of said prism is transmitted,with the angle formed by said first reflection surface and said secondreflection surface set within a range of 40° or more and less than 45°and is constituted of a low-dispersion optical material with an Abbenumber of 65 or higher; and the surface position of the detection targetsurface is detected based upon an output from said detection unit.
 26. Asurface position detection device according to claim 25, wherein: saidprism is constituted of an optical material having a coefficient ofthermal expansion equal to or lower than 1 ppm/K, which does not expandreadily in heat.
 27. A surface position detection device for detecting asurface position of a detection target surface, comprising; a projectionsystem that projects a light flux from a diagonal direction onto thedetection target surface; a light-receiving system that receives a lightflux having been reflected at the detection target surface; and a meansfor light flux deflection provided, at least, either in an optical pathof said projection system or in an optical path of said light-receivingsystem and having an even number of reflection surfaces to allow anincident light flux to exit at an angle that is not parallel to theincident light flux, which includes a pair of reflection mirrors thatare not parallel to each other and holding members each provided tointerfit with and hold one of said pair of reflecting mirrors, wherein:the surface position of the detection target surface is detected basedupon an output from said light-receiving system.
 28. A surface positiondetection device according to claim 27, wherein: said holding membersare constituted of an optical material having a coefficient of thermalexpansion equal to or lower than 1 ppm/K, which does not expand readilyin heat.
 29. A surface position detection device for detecting a surfaceposition of a detection target surface, comprising; a projection systemthat projects a light flux from a diagonal direction onto the detectiontarget surface and includes a projection optical system provided to forma primary image of a specific pattern onto the detection target surface;a light-receiving system that receives a light flux having beenreflected at the detection target surface and includes a condenseroptical system provided to form a secondary image of the specificpattern by condensing the light flux having been reflected at thedetection target surface and a detection unit provided to detect thesecondary image of the specific pattern formed via said condenseroptical system; a means for light flux deflection provided, at least,either in an optical path of said projection system or in an opticalpath of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux, which includes a pairof reflection mirrors that are not parallel to each other and holdingmembers each provided to interfit with and hold one of said pair ofreflecting mirrors; wherein the surface position of the detection targetsurface is detected based upon an output from said detection unit.
 30. Asurface position detection device according to claim 29, wherein: saidholding members are constituted of an optical material having acoefficient of thermal expansion equal to or lower than 1 ppm/K, whichdoes not expand readily in heat.
 31. An exposure apparatus that performsprojection exposure of a pattern formed at a mask onto a photosensitivesubstrate via a projection optical system, comprising; a surfaceposition detection device that detects a surface position of the patternsurface at the mask or an exposure target surface of the photosensitivesubstrate relative to said projection optical system as a surfaceposition of a detection target surface and includes; a projection systemthat projects a light flux from a diagonal direction onto the detectiontarget surface; a light-receiving system that receives a light fluxhaving been reflected at the detection target surface; and a means forlight flux deflection provided, at least, either in an optical path ofsaid projection system or in an optical path of said light-receivingsystem and having an even number of reflection surfaces to allow anincident light flux to exit at an angle that is not parallel to theincident light flux; to detect the surface position of the detectiontarget surface is based upon an output from said light-receiving system;and a means for alignment that aligns the pattern surface at the mask orthe exposure target surface of the photosensitive substrate relative tosaid projection optical system based upon results of a detectionperformed by said surface position detection device.
 32. An exposureapparatus that performs projection exposure of a pattern formed at amask onto a photosensitive substrate via a projection optical system,comprising; a surface position detection device that detects a surfaceposition of the pattern surface at the mask or an exposure targetsurface of the photosensitive substrate relative to said projectionoptical system as a surface position of a detection target surface andincludes; a projection system that projects a light flux from a diagonaldirection onto the detection target surface; a light-receiving systemthat receives a light flux having been reflected at the detection targetsurface; and a means for light flux deflection provided, at least,either in an optical path of said projection system or in an opticalpath of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux, which includes a prismhaving a pair of reflection surfaces that are not parallel to eachother; to detect the surface position of the detection target surface isdetected based upon an output from said light-receiving system; and ameans for alignment that aligns the pattern surface at the mask or theexposure target surface of the photosensitive substrate relative to saidprojection optical system based upon results of a detection performed bysaid surface position detection device.
 33. An exposure apparatusaccording to claim 32, wherein: said prism is constituted of an opticalmaterial having a coefficient of thermal expansion equal to or lowerthan 1 ppm/K, which does not expand readily in heat.
 34. An exposureapparatus that performs projection exposure of a pattern formed at amask onto a photosensitive substrate via a projection optical system,comprising; a surface position detection device that detects a surfaceposition of the pattern surface at the mask or an exposure targetsurface of the photosensitive substrate relative to said projectionoptical system as a surface position of a detection target surface andincludes; a projection system that projects a light flux from a diagonaldirection onto the detection target surface; a light-receiving systemthat receives a light flux having been reflected at the detection targetsurface; and a means for light flux deflection provided, at least,either in an optical path of said projection system or in an opticalpath of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux, which includes a prismhaving a pair of reflection surfaces that are not parallel to each otherand constituted of a low-dispersion optical material with an Abbe numberof 65 or higher; to detect the surface position of the detection targetsurface based upon a output from said light-receiving system and; ameans for alignment that aligns the pattern surface at the mask or theexposure target surface of the photosensitive substrate relative to saidprojection optical system based upon results of a detection performed bysaid surface position detection device.
 35. An exposure apparatusaccording to claim 34, wherein: said prism is constituted of an opticalmaterial having a coefficient of thermal expansion equal to or lowerthan 1 ppm/K, which does not expand readily in heat.
 36. An exposureapparatus that performs projection exposure of a pattern formed at amask onto a photosensitive substrate via a projection optical system,comprising; a surface position detection device that detects a surfaceposition of the pattern surface at the mask or an exposure targetsurface of the photosensitive substrate relative to said projectionoptical system as a surface position of a detection target surface andincludes; a projection system that projects a light flux from a diagonaldirection onto the detection target surface; a light-receiving systemthat receives a light flux having been reflected at the detection targetsurface; and a means for light flux deflection provided, at least,either in an optical path of said projection system or in an opticalpath of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux, which includes a prismhaving a pair of reflection surfaces that are not parallel to eachother, with said prism having a first transmission surface through whichthe incident light flux is transmitted, a first reflection surface atwhich the light flux having been transmitted through said firsttransmission surface and propagated through the inside of said prism isreflected, a second reflection surface at which the light flux havingbeen reflected at said first reflection surface and propagated throughthe inside of said prim is reflected along an optical path intersectingthe optical path of the light flux having been transmitted through saidfirst transmission surface and a second transmission surface throughwhich the light flux having been reflected at said second reflectionsurface and propagated through the inside of said prism is transmitted;to detect the surface position of the detection target surface basedupon an output from said light-receiving system and; a means foralignment that aligns the pattern surface at the mask or the exposuretarget surface of the photosensitive substrate relative to saidprojection optical system based upon results of a detection performed bysaid surface position detection device.
 37. An exposure apparatusaccording to claim 36, wherein: said prism is constituted of an opticalmaterial having a coefficient of thermal expansion equal to or lowerthan 1 ppm/K, which does not expand readily in heat.
 38. An exposureapparatus that performs projection exposure of a pattern formed at amask onto a photosensitive substrate via a projection optical system,comprising; a surface position detection device that detects a surfaceposition of the pattern surface at the mask or an exposure targetsurface of the photosensitive substrate relative to said projectionoptical system as a surface position of a detection target surface andincludes, a projection system that projects a light flux from a diagonaldirection onto the detection target surface; a light-receiving systemthat receives a light flux having been reflected at the detection targetsurface; and a means for light flux deflection provided, at least,either in an optical path of said projection system or in an opticalpath of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux, which includes a prismhaving a pair of reflection surfaces that are not parallel to eachother, with said prism having a first transmission surface through whichthe incident light flux is transmitted, a first reflection surface atwhich the light flux having been transmitted through said firsttransmission surface and propagated through the inside of said prism isreflected, a second reflection surface at which the light flux havingbeen reflected at said first reflection surface and propagated throughthe inside of said prim is reflected along an optical path intersectingthe optical path of the light flux having been transmitted through saidfirst transmission surface and a second transmission surface throughwhich the light flux having been reflected at said second reflectionsurface and propagated through the inside of said prism is transmittedand constituted of a low-dispersion optical material with an Abbe numberof 65 or higher; to detect the surface position of the detection targetsurface is detected based upon an output from said light-receivingsystem and; a means for alignment that aligns the pattern surface at themask or the exposure target surface of the photosensitive substraterelative to said projection optical system based upon results of adetection performed by said surface position detection device.
 39. Anexposure apparatus according to claim 38, wherein: said prism isconstituted of an optical material having a coefficient of thermalexpansion equal to or lower than 1 ppm/K, which does not expand readilyin heat.
 40. An exposure apparatus that performs projection exposure ofa pattern formed at a mask onto a photosensitive substrate via aprojection optical system, comprising; a surface position detectiondevice that detects a surface position of the pattern surface at themask or an exposure target surface of the photosensitive substraterelative to said projection optical system as a surface position of adetection target surface and includes; a projection system that projectsa light flux from a diagonal direction onto the detection targetsurface; a light-receiving system that receives a light flux having beenreflected at the detection target surface; and a means for light fluxdeflection provided, at least, either in an optical path of saidprojection system or in an optical path of said light-receiving systemand having an even number of reflection surfaces to allow an incidentlight flux to exit at an angle that is not parallel to the incidentlight flux, which includes a prism having a pair of reflection surfacesthat are not parallel to each other, with said prism having a firsttransmission surface through which the incident light flux istransmitted, a first reflection surface at which the light flux havingbeen transmitted through said first transmission surface and propagatedthrough the inside of said prism is reflected, a second reflectionsurface at which the light flux having been reflected at said firstreflection surface and propagated through the inside of said prim isreflected along an optical path intersecting the optical path of thelight flux having been transmitted through said first transmissionsurface and a second transmission surface through which the light fluxhaving been reflected at said second reflection surface and propagatedthrough the inside of said prism is transmitted and the angle formed bysaid first reflection surface and said second reflection surface setwithin a range of 40° or greater and less than 45°; to detect thesurface position of the detection target surface is detected based uponan output from said light-receiving system and; a means for alignmentthat aligns the pattern surface at the mask or the exposure targetsurface of the photosensitive substrate relative to said projectionoptical system based upon results of a detection performed by saidsurface position detection device.
 41. An exposure apparatus accordingto claim 40, wherein: said prism is constituted of an optical materialhaving a coefficient of thermal expansion equal to or lower than 1ppm/K, which does not expand readily in heat.
 42. An exposure apparatusthat performs projection exposure of a pattern formed at a mask onto aphotosensitive substrate via a projection optical system, comprising; asurface position detection device tat detects a surface position of thepattern surface at the mask or an exposure target surface of thephotosensitive substrate relative to said projection optical system as asurface position of a detection target surface and includes; aprojection system that projects a light flux from a diagonal directiononto the detection target surface; a light-receiving system thatreceives a light flux having been reflected at the detection targetsurface; and a means for light flux deflection provided, at least,either in an optical path of said projection system or in an opticalpath of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux, which includes a prismhaving a pair of reflection surfaces that are not parallel to eachother, with said prism having a first transmission surface through whichthe incident light flux is transmitted, a first reflection surface atwhich the light flux having been transmitted through said firsttransmission surface and propagated through the inside of said prism isreflected, a second reflection surface at which the light flux havingbeen reflected at said first reflection surface and propagated throughthe inside of said prim is reflected along an optical path intersectingthe optical path of the light flux having been transmitted through saidfirst transmission surface and a second transmission surface throughwhich the light flux having been reflected at said second reflectionsurface and propagated through the inside of sad prism is transmitted,the angle formed by said first reflection surface and said secondreflection surface set within a range of 40° or greater and less than45° and said prism is constituted of a low-dispersion optical materialwith an Abbe number of 65 or greater; to detect the surface position ofthe detection target surface based upon an output from saidlight-receiving system and; a means for alignment that aligns thepattern surface at the mask or the exposure target surface of thephotosensitive substrate relative to said projection optical systembased upon results of a detection performed by said surface positiondetection device.
 43. An exposure apparatus according to claim 42,wherein: said prism is constituted of an optical material having acoefficient of thermal expansion equal to or lower than 1 ppm/K, whichdoes not expand readily in heat.
 44. An exposure apparatus that performsprojection exposure of a pattern formed at a mask onto a photosensitivesubstrate via a projection optical system, comprising; a surfaceposition detection device that detects a surface position of the patternsurface at the mask or an exposure target surface of the photosensitivesubstrate relative to said projection optical system as a surfaceposition of a detection target surface and includes; a projection systemthat projects a light flux from a diagonal direction onto the detectiontarget surface and includes a projection optical system provided to forma primary image of a specific pattern onto the detection target surface;a light-receiving system that receives a light flux having beenreflected at the detection target surface and includes a condenseroptical system provided to form a secondary image of the specificpattern by condensing a light flux having been reflected at thedetection target surface and a detection unit provided to detect thesecondary image of the specific pattern formed via said condenseroptical system; and a means for light flux deflection provided, atleast, either in an optical path of said projection system or in anoptical path of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux; to detect the surfaceposition of the detection target surface based upon an output from saiddetection unit and; a means for alignment that aligns the patternsurface at the mask or the exposure target surface of the photosensitivesubstrate relative to said projection optical system based upon resultsof a detection performed by said surface position detection device. 45.An exposure apparatus that performs projection exposure of a patternformed at a mask onto a photosensitive substrate via a projectionoptical system, comprising; a surface position detection device thatdetects a surface position of the pattern surface at the mask or anexposure target surface of the photosensitive substrate relative to saidprojection optical system as a surface position of a detection targetsurface and includes; a projection system that projects a light fluxfrom a diagonal direction onto the detection target surface and includesa projection optical system provided to form a primary image of aspecific pattern onto the detection target surface; a light-receivingsystem that receives a light flux having been reflected at the detectiontarget surface and includes a condenser optical system provided to forma secondary image of the specific pattern by condensing a light fluxhaving been reflected at the detection target surface and a detectionunit provided to detect the secondary image of the specific patternformed via said condenser optical system; and a means for light fluxdeflection provided, at least, either in an optical path of saidprojection system or in an optical path of said light-receiving systemand having an even number of reflection surfaces to allow an incidentlight flux to exit at an angle that is not parallel to the incidentlight flux, which includes a prism having a pair of reflection surfacesthat are not parallel to each other; to detect the surface position ofthe detection target surface based upon an output from said detectionunit and; a means for alignment that aligns the pattern surface at themask or the exposure target surface of the photosensitive substraterelative to said projection optical system based upon results of adetection performed by said surface position detection device.
 46. Anexposure apparatus according to claim 45, wherein: said prism isconstituted of an optical material having a coefficient of thermalexpansion equal to or lower than 1 ppm/K, which does not expand readilyin heat.
 47. An exposure apparatus that performs projection exposure ofa pattern formed at a mask onto a photosensitive substrate via aprojection optical system, comprising; a surface position detectiondevice that detects a surface position of the pattern surface at themask or an exposure target surface of the photosensitive substraterelative to sad projection optical system as a surface position of adetection target surface and includes; a projection system that projectsa light flux from a diagonal direction onto the detection target surfaceand includes a projection optical system provided to form a primaryimage of a specific pattern onto the detection target surface; alight-receiving system that receives a light flux having been reflectedat the detection target surface and includes a condenser optical systemprovided to form a secondary image of the specific pattern by condensinga light flux having been reflected at the detection target surface and adetection unit provided to detect the secondary image of the specificpattern formed via said condenser optical system; and a means for lightflux deflection provided, at least, either in an optical path of saidprojection system or in an optical path of said light-receiving systemand having an even number of reflection surfaces to allow an incidentlight flux to exit at an angle that is not parallel to the incidentlight flux, which includes a prism having a pair of reflection surfacesthat are not parallel to each other and constituted of a low-dispersionoptical material with an Abbe number of 65 or higher; to detect thesurface position of the detection target surface based upon an outputfrom said detection unit and; a means for alignment that aligns thepattern surface at the mask or the exposure target surface of thephotosensitive substrate relative to said projection optical systembased upon results of a detection performed by said surface positiondetection device.
 48. An exposure apparatus according to claim 47,wherein: said prism is constituted of an optical material having acoefficient of thermal expansion equal to or lower than 1 ppm/K, whichdoes not expand readily in heat.
 49. An exposure apparatus that performsprojection exposure of a pattern formed at a mask onto a photosensitivesubstrate via a projection optical system, comprising; a surfaceposition detection device that detects a surface position of the patternsurface at the mask or an exposure target surface of the photosensitivesubstrate relative to said projection optical system as a surfaceposition of a detection target surface and includes; a projection systemthat projects a light flux from a diagonal direction onto the detectiontarget surface and includes a projection optical system provided to forma primary image of a specific pattern onto the detection target surface;a light-receiving system that receives a light flux having beenreflected at the detection target surface and includes a condenseroptical system provided to form a secondary image of the specificpattern by condensing a light flux having been reflected at thedetection target surface and a detection unit provided to detect thesecondary image of the specific pattern formed via said condenseroptical system; and a means for light flux deflection provided, atleast, either in an optical path of said projection system or in anoptical path of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux, which includes a prismhaving a pair of reflection surfaces that are not parallel to eachother, with said prism having a first transmission surface through whichthe incident light flux is transmitted, a first reflection surface atwhich the light flux having been transmitted through said firsttransmission surface and propagated through the inside of said prism isreflected, a second reflection surface at which the light flux havingbeen reflected at said first reflection surface and propagated throughthe inside of said prim is reflected along an optical path intersectingthe optical path of the light flux having been transmitted through saidfirst transmission surface and a second transmission surface throughwhich the light flux having been reflected at said second reflectionsurface and propagated through the inside of said prism is transmitted;to detect the surface position of the detection target surface basedupon an output from said detection unit and; a means for alignment thataligns the pattern surface at the mask or the exposure target surface ofthe photosensitive substrate relative to said projection optical systembased upon results of a detection performed by said surface positiondetection device.
 50. An exposure apparatus according to claim 49,wherein: said prism is constituted of an optical material having acoefficient of thermal expansion equal to or lower than 1 ppm/K, whichdoes not expand readily in heat.
 51. An exposure apparatus that performsprojection exposure of a pattern formed at a mask onto a photosensitivesubstrate via a projection optical system, comprising; a surfaceposition detection device that detects a surface position of the patternsurface at the mask or an exposure target surface of the photosensitivesubstrate relative to said projection optical system as a surfaceposition of a detection target surface and includes; a projection systemthat projects a light flux from a diagonal direction onto the detectiontarget surface and includes a projection optical system provided to forma primary image of a specific pattern onto the detection target surface;a light-receiving system that receives a light flux having beenreflected at the detection target surface and includes a condenseroptical system provided to form a secondary image of the specificpattern by condensing a light flux having been reflected at thedetection target surface and a detection unit provided to detect thesecondary image of the specific pattern formed via said condenseroptical system; and a means for light flux deflection provided, atleast, either in an optical path of said projection system or in anoptical path of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux, which includes a prismhaving a pair of reflection surfaces that are not parallel to eachother, with said prism having a first transmission surface through whichthe incident, light flux is transmitted, a first reflection surface atwhich the light flux having been transmitted through said firsttransmission surface and propagated through the inside of said prism isreflected, a second reflection surface at which the light flux havingbeen reflected at said first reflection surface and propagated throughthe inside of said prim is reflected along an optical path intersectingthe optical path of the light flux having been transmitted through saidfirst transmission surface and a second transmission surface throughwhich the light flux having been reflected at said second reflectionsurface and propagated through the inside of said prism is transmittedand constituted of a low-dispersion optical material with an Abbe numberof 65 or higher; to detect the surface position of the detection targetsurface based upon an output from said detection unit and; a means foralignment that aligns the pattern surface at the mask or the exposuretarget surface of the photosensitive substrate relative to saidprojection optical system based upon results of a detection performed bysaid surface position detection device.
 52. An exposure apparatusaccording to claim 51, wherein: said prism is constituted of an opticalmaterial having a coefficient of thermal expansion equal to or lowerthan 1 ppm/K, which does not expand readily in heat.
 53. An exposureapparatus that performs projection exposure of a pattern formed at amask onto a photosensitive substrate via a projection optical system,comprising; a surface position detection device that detects a surfaceposition of the pattern surface at the mask or an exposure targetsurface of the photosensitive substrate relative to said projectionoptical system as a surface position of a detection target surface andincludes; a projection system that projects a light flux from a diagonaldirection onto the detection target surface and includes a projectionoptical system provided to form a primary image of a specific patternonto the detection target surface; a light-receiving system thatreceives a light flux having been reflected at the detection targetsurface and includes a condenser optical system provided to form asecondary image of the specific pattern by condensing a light fluxhaving been reflected at the detection target surface and a detectionunit provided to detect the secondary image of the specific patternformed via said condenser optical system; and a means for light fluxdeflection provided, at least, either in an optical path of saidprojection system or in an optical path of said light-receiving systemand having an even number of reflection surfaces to allow an incidentlight flux to exit at an angle that is not parallel to the incidentlight flux, which includes a prism having a pair of reflection surfacesthat are not parallel to each other, with said prism having a firsttransmission surface through which the incident light flux istransmitted, a first reflection surface at which the light flux havingbeen transmitted through said first transmission surface and propagatedthrough the inside of said prism is reflected, a second reflectionsurface at which the light flux having been reflected at said firstreflection surface and propagated through the inside of said prim isreflected along an optical path intersecting the optical path of thelight flux having been transmitted through said first transmissionsurface and a second transmission surface through which the light fluxhaving been reflected at said second reflection surface and propagatedthrough the inside of said prism is transmitted and the angle formed bysaid first reflection surface and said second reflection surface setwithin a range of 40° or greater and less than 45°; to detect thesurface position of the detection target surface based upon an outputfrom said detection unit and; a means for alignment that aligns thepattern surface at the mask or the exposure target surface of thephotosensitive substrate relative to said projection optical systembased upon results of a detection performed by said surface positiondetection device.
 54. An exposure apparatus according to claim 53,wherein: said prism is constituted of an optical material having acoefficient of thermal expansion equal to or lower than 1 ppm/K, whichdoes not expand readily in heat.
 55. An exposure apparatus that performsprojection exposure of a pattern formed at a mask onto a photosensitivesubstrate via a projection optical system, comprising; a surfaceposition detection device that detects a surface position of the patternsurface at the mask or an exposure target surface of the photosensitivesubstrate relative to said projection optical system as a surfaceposition of a detection target surface and includes; a projection systemthat projects a light flux from a diagonal direction onto the detectiontarget surface and includes a projection optical system provided to forma primary image of a specific pattern onto the detection target surface;a light-receiving system that receives a light flux having beenreflected at the detection target surface and includes a condenseroptical system provided to form a secondary image of the specificpattern by condensing a light flux having been reflected at thedetection target surface and a detection unit provided to detect thesecondary image of the specific pattern formed via said condenseroptical system; and a means for light flux deflection provided, atleast, either in an optical path of said projection system or in anoptical path of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux, which includes a prismhaving a pair of reflection surfaces that are not parallel to eachother, with said prism having a first transmission surface through whichthe incident light flux is transmitted, a first reflection surface atwhich the light flux having been transmitted through said firsttransmission surface and propagated through the inside of said prism isreflected, a second reflection surface at which the light flux havingbeen reflected at said first reflection surface and propagated throughthe inside of said prim is reflected along an optical path intersectingthe optical path of the light flux having been transmitted through saidfirst transmission surface and a second transmission surface throughwhich the light flux having been reflected at said second reflectionsurface and propagated through the inside of said prism is transmitted,the angle formed by said first reflection surface and said secondreflection surface set within a range of 40° or greater and less than45° and said prism is constituted of a low-dispersion optical materialwith an Abbe number of 65 or greater; to detect the surface position ofthe detection target surface based upon an output from said detectionunit and; a means for alignment that aligns the pattern surface at themask or the exposure target surface of the photosensitive substraterelative to said projection optical system based upon results of adetection performed by said surface position detection device.
 56. Anexposure apparatus according to claim 55, wherein: said prism isconstituted of an optical material having a coefficient of thermalexpansion equal to or lower than 1 ppm/K, which does not expand readilyin heat.
 57. An exposure apparatus that performs projection exposure ofa pattern formed at a mask onto a photosensitive substrate via aprojection optical system, comprising; a surface position detectiondevice that detects a surface position of the pattern surface at themask or an exposure target surface of the photosensitive substraterelative to said projection optical system as a surface position of adetection target surface and includes; a projection system that projectsa light flux from a diagonal direction onto the detection targetsurface; a light-receiving system that receives a light flux having beenreflected at the detection target surface; and a means for light fluxdeflection provided, at least, either in an optical path of saidprojection system or in an optical path of said light-receiving systemand having an even number of reflection surfaces to allow an incidentlight flux to exit at an angle that is not parallel to the incidentlight flux, which includes a pair of reflection mirrors that are notparallel to each other and holding members each provided to interfitwith and hold one of said pair of reflecting mirrors; to detect thesurface position of the detection target surface based upon an outputfrom said light-receiving system; and a means for alignment that alignsthe pattern surface at the mask or the exposure target surface of thephotosensitive substrate relative to said projection optical systembased upon results of a detection performed by said surface positiondetection device.
 58. An exposure apparatus according to claim 57,wherein: said holding members are constituted of an optical materialhaving a coefficient of thermal expansion equal to or lower than 1ppm/K, which does not expand readily in heat.
 59. An exposure apparatusthat performs projection exposure of a pattern formed at a mask onto aphotosensitive substrate via a projection optical system, comprising; asurface position detection device that detects a surface position of thepattern surface at the mask or an exposure target surface of thephotosensitive substrate relative to said projection optical system as asurface position of a detection target surface and includes; aprojection system that projects a light flux from a diagonal directiononto the detection target surface and includes a projection opticalsystem provided to form a primary image of a specific pattern onto thedetection target surface; a light-receiving system that receives a lightflux having been reflected at the detection target surface and includesa condenser optical system provided to form a secondary image of thespecific pattern by condensing the light flux having been reflected atthe detection target surface and a detection unit provided to detect thesecondary image of the specific pattern formed via said condenseroptical system; a means for light flux deflection provided, at least,either in an optical path of said projection system or in an opticalpath of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux, which includes a pairof reflection mirrors that are not parallel to each other and holdingmembers each provided to interfit with and hold one of said pair ofreflecting mirrors; to detect the surface position of the detectiontarget surface based upon an output from said detection unit; and ameans for alignment that aligns the pattern surface at the mask or theexposure target surface of the photosensitive substrate relative to saidprojection optical system based upon results of a detection performed bysaid surface position detection device.
 60. An exposure apparatusaccording to claim 59, wherein: said holding members are constituted ofan optical material having a coefficient of thermal expansion equal toor lower than 1 ppm/K, which does not expand readily in heat.
 61. Anexposure method for implementing projection exposure of a pattern formedat a mask onto a photosensitive substrate via a projection opticalsystem, comprising; a detection step in which the surface position of apattern surface of the mask or an exposure target surface of thephotosensitive substrate relative to said projection optical system isdetected as a surface position of a detection target surface byemploying a surface position detection device that detects the surfaceposition of the detection target surface and includes; a projectionsystem that projects a light flux from a diagonal direction onto thedetection target surface; a light-receiving system that receives a lightflux having been reflected at the detection target surface; and a meansfor light flux deflection provided, at least, either in an optical pathof sad projection system or in an optical path of said light-receivingsystem and having an even number of reflection surfaces to allow anincident light flux to exit at an angle that is not parallel to theincident light flux; to detect the surface position of the detectiontarget surface based upon an output from said light-receiving system;and an alignment step in which the pattern surface of the mask or theexposure target surface of the photosensitive substrate is alignedrelative to said projection optical system based upon results of adetection performed in said detection step.
 62. An exposure method forimplementing projection exposure of a pattern formed at a mask onto aphotosensitive substrate via a projection optical system, comprising; adetection step in which the surface position of a pattern surface of themask or an exposure target surface of the photosensitive substraterelative to said projection optical system is detected as a surfaceposition of a detection target surface by employing a surface positiondetection device that detects the surface position of the detectiontarget surface and includes; a projection system that projects a lightflux from a diagonal direction onto the detection target surface; alight-receiving system that receives a light flux having been reflectedat the detection target surface; and a means for light flux deflectionprovided, at least, either in an optical path of said projection systemor in an optical path of said light-receiving system and having an evennumber of reflection surfaces to allow an incident light flux to exit atan angle that is not parallel to the incident light flux, which includesa prism having a pair of reflection surfaces that are not parallel toeach other; to detect the surface position of the detection targetsurface based upon an output from said light-receiving system; and analignment step in which the pattern surface of the mask or the exposuretarget surface of the photosensitive substrate is aligned relative tosaid projection optical system based upon results of a detectionperformed in said detection step.
 63. An exposure method according toclaim 62, wherein: said prism is constituted of an optical materialhaving a coefficient of thermal expansion equal to or lower than 1ppm/K, which does not expand readily in heat.
 64. An exposure method forimplementing projection exposure of a pattern formed at a mask onto aphotosensitive substrate via a projection optical system, comprising; adetection step in which the surface position of a pattern surface of themask or an exposure target surface of the photosensitive substraterelative to said projection optical system is detected as a surfaceposition of a detection target surface by employing a surface positiondetection device that detects the surface position of the detectiontarget surface and includes; a projection system that projects a lightflux from a diagonal direction onto the detection target surface; alight-receiving system that receives a light flux having been reflectedat the detection target surface; and a means for light flux deflectionprovided, at least, either in an optical path of said projection systemor in an optical path of said light-receiving system and having an evennumber of reflection surfaces to allow an incident light flux to exit atau angle that is not parallel to the incident light flux, which includesa prism having a pair of reflection surfaces that are not parallel toeach other and constituted of a low-dispersion optical material with anAbbe number of 65 or higher; to detect the surface position of thedetection target surface based upon an output from said light-receivingsystem; and an alignment step in which the pattern surface of the maskor the exposure target surface of the photosensitive substrate isaligned relative to said projection optical system based upon results ofa detection performed in said detection step.
 65. An exposure methodaccording to claim 64, wherein: said prism is constituted of an opticalmaterial having a coefficient of thermal expansion equal to or lowerthan 1 ppm/K, which does not expand readily in heat.
 66. An exposuremethod for implementing projection exposure of a pattern formed at amask onto a photosensitive substrate via a projection optical system,comprising; a detection step in which the surface position of a patternsurface of the mask or an exposure target surface of the photosensitivesubstrate relative to said projection optical system is detected as asurface position of a detection target surface by employing a surfaceposition detection device that detects the surface position of thedetection target surface and includes; a projection system that projectsa light flux from a diagonal direction onto the detection targetsurface; a light-receiving system that receives a light flux having beenreflected at the detection target surface; and a means for light fluxdeflection provided, at least, either in an optical path of saidprojection system or in an optical path of said light-receiving systemand having an even number of reflection surfaces to allow an incidentlight flux to exit at an angle that is not parallel to the incidentlight flux, which includes a prism having a pair of reflection surfacesthat are not parallel to each other, with said prism having a firsttransmission surface through which the incident light flux istransmitted, a first reflection surface at which the light flux havingbeen transmitted through said first transmission surface and propagatedthrough the inside of said prism is reflected, a second reflectionsurface at which the light flux having been reflected at said firstreflection surface and propagated through the inside of said prim isreflected along an optical path intersecting the optical path of thelight flux having been transmitted through said first transmissionsurface and a second transmission surface through which the light fluxhaving been reflected at said second reflection surface and propagatedthrough the inside of said prism is transmitted; to detect the surfaceposition of the detection target surface based upon an output from saidlight-receiving system; and an alignment step in which the patternsurface of the mask or the exposure target surface of the photosensitivesubstrate is aligned relative to said projection optical system basedupon results of a detection performed in said detection step.
 67. Anexposure method according to claim 66, wherein: said prism isconstituted of an optical material having a coefficient of thermalexpansion equal to or lower than 1 ppm/K, which does not expand readilyin heat.
 68. An exposure method for implementing projection exposure ofa pattern formed at a mask onto a photosensitive substrate via aprojection optical system, comprising; a detection step in which thesurface position of a pattern surface of the mask or an exposure targetsurface of the photosensitive substrate relative to said projectionoptical system is detected as a surface position of a detection targetsurface by employing a surface position detection device that detectsthe surface position of the detection target surface and includes; aprojection system that projects a light flux from a diagonal directiononto the detection target surface; a light-receiving system thatreceives a light flux having been reflected at the detection targetsurface; and a means for light flux deflection provided, at least,either in an optical path of said projection system or in an opticalpath of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux, which includes a prismhaving a pair of reflection surfaces that are not parallel to eachother, a first transmission surface through which the incident lightflux is transmitted, a first reflection surface at which the light fluxhaving been transmitted through said first transmission surface andpropagated through the inside of said prism is reflected, a secondreflection surface at which the light flux having been reflected at saidfirst reflection surface and propagated through the inside of said primis reflected along an optical path intersecting the optical path of thelight flux having been transmitted through said first transmissionsurface and a second transmission surface through which the light fluxhaving been reflected at said second reflection surface and propagatedthrough the inside of said prism is transmitted, and constituted of alow-dispersion optical material with an Abbe number of 65 or higher; todetect the surface position of the detection target surface based uponan output from said light-receiving system; and an alignment step inwhich the pattern surface of the mask or the exposure target surface ofthe photosensitive substrate is aligned relative to said projectionoptical system based upon results of a detection performed in saiddetection step.
 69. An exposure method according to claim 68, wherein:said prism is constituted of an optical material having a coefficient ofthermal expansion equal to or lower than 1 ppm/K, which does not expandreadily in heat.
 70. An exposure method for implementing projectionexposure of a pattern formed at a mask onto a photosensitive substratevia a projection optical system, comprising; a detection step in whichthe surface position of a pattern surface of the mask or an exposuretarget surface of the photosensitive substrate relative to saidprojection optical system is detected as a surface position of adetection target surface by employing a surface position detectiondevice that detects the surface position of the detection target surfaceand includes; a projection system that projects a light flux from adiagonal direction onto the detection target surface; a light-receivingsystem that receives a light flux having been reflected at the detectiontarget surface; and a means for light flux deflection provided, atleast, either in an optical path of said projection system or in anoptical path of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux, which includes a prismhaving a pair of reflection surfaces that are not parallel to eachother, a first transmission surface through which the incident lightflux is transmitted, a first reflection surface at which the light fluxhaving been transmitted through said first transmission surface andpropagated through the inside of said prism is reflected, a secondreflection surface at which the light flux having been reflected at saidfirst reflection surface and propagated through the inside of said primis reflected along an optical path intersecting the optical path of thelight flux having been transmitted through said first transmissionsurface and a second transmission surface through which the light fluxhaving been reflected at said second reflection surface and propagatedthrough the inside of said prism is transmitted, and the angle formed bysaid first reflection surface and said second reflection surface setwithin a range of 40° or greater and less than 45°; to detect thesurface position of the detection target surface based upon an outputfrom said light-receiving system; and an alignment step in which thepattern surface of the mask or the exposure target surface of thephotosensitive substrate is aligned relative to said projection opticalsystem based upon the results of a detection performed in said detectionstep.
 71. An exposure method according to claim 70, wherein; said prismis constituted of an optical material having a coefficient of thermalexpansion equal to or lower than 1 ppm/K, which does not expand readilyin heat.
 72. An exposure method for implementing projection exposure ofa pattern formed at a mask onto a photosensitive substrate via aprojection optical system, comprising; a detection step in which thesurface position of a pattern surface of the mask or an exposure targetsurface of the photosensitive substrate relative to said projectionoptical system is detected as a surface position of a detection targetsurface by employing a surface position detection device that detectsthe surface position of the detection target surface and includes; aprojection system that projects a light flux from a diagonal directiononto the detection target surface; a light-receiving system thatreceives a light flux having been reflected at the detection targetsurface; and a means for light flux deflection provided, at least,either in an optical path of said projection system or in an opticalpath of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux, which includes a prismhaving a pair of reflection surfaces that are not parallel to eachother, a first transmission surface through which the incident lightflux is transmitted, a first reflection surface at which the light fluxhaving been transmitted through said first transmission surface andpropagated through the inside of said prism is reflected, a secondreflection surface at which the light flux having been reflected at saidfirst reflection surface and propagated through the inside of said prismis reflected along an optical path intersecting the optical path of thelight flux having been transmitted through said first transmissionsurface and a second transmission surface through which the light fluxhaving been reflected at said second reflection surface and propagatedthrough the inside of said prism is transmitted, and the angle formed bysaid first reflection surface and said second reflection surface setwithin a range of 40° or greater and less than 45° and said prism isconstituted of a low-dispersion optical material with an Abbe number of65 or higher; to detect the surface position of the detection targetsurface based upon an output from said light-receiving system; and analignment step in which the pattern surface of the mask or the exposuretarget surface of the photosensitive substrate is aligned relative tosaid projection optical system based upon the results of a detectionperformed in said detection step.
 73. An exposure method according toclaim 72, wherein: said prism is constituted of an optical materialhaving a coefficient of thermal expansion equal to or lower than 1ppm/K, which does not expand readily in heat.
 74. An exposure method forimplementing projection exposure of a pattern formed at a mask onto aphotosensitive substrate via a projection optical system, comprising; adetection step in which the surface position of a pattern surface of themask or an exposure target surface of the photosensitive substraterelative to said projection optical system is detected as a surfaceposition of a detection target surface by employing a surface positiondetection device that detects the surface position of the detectiontarget surface and includes; a projection system that projects a lightflux from a diagonal direction onto the detection target surface andincludes a projection optical system provided to form a primary image ofa specific pattern onto the detection target surface; a light-receivingsystem that receives a light flux having been reflected at the detectiontarget surface and includes a condenser optical system provided to forma secondary image of the specific pattern by condensing the light fluxhaving been reflected at the detection target surface and a detectionunit provided to detect the secondary image of the specific patternformed via said condenser optical system; and a means for light fluxdeflection provided, at least, either in an optical path of saidprojection system or in an optical path of said light-receiving systemand having an even number of reflection surfaces to allow an incidentlight flux to exit at an angle that is not parallel to the incidentlight flux; to detect the surface position of the detection targetsurface based upon an output from said detection unit; and an alignmentstep in which the pattern surface of the mask or the exposure targetsurface of the photosensitive substrate is aligned relative to saidprojection optical system based upon results of a detection performed insaid detection step.
 75. An exposure method for implementing projectionexposure of a pattern formed at a mask onto a photosensitive substratevia a projection optical system, comprising; a detection step in whichthe surface position of a pattern surface of the mask or an exposuretarget surface of the photosensitive substrate relative to saidprojection optical system is detected as a surface position of adetection target surface by employing a surface position detectiondevice that detects the surface position of the detection target surfaceand includes; a projection system that projects a light flux from adiagonal direction onto the detection target surface and includes aprojection optical system provided to form a primary image of a specificpattern onto the detection target surface; a light-receiving system thatreceives a light flux having been reflected at the detection targetsurface and includes a condenser optical system provided to form asecondary image of the specific pattern by condensing the light fluxhaving been reflected at the detection target surface and a detectionunit provided to detect the secondary image of the specific patternformed via said condenser optical system; and a means for light fluxdeflection provided, at least, either in an optical path of saidprojection system or in an optical path of said light-receiving systemand having an even number of reflection surfaces to allow an incidentlight flux to exit at an angle that is not parallel to the incidentlight flux which includes a prism having a pair of reflection surfacesthat are not parallel to each other; to detect the surface position ofthe detection target surface based upon an output from said detectionunit; and an alignment step in which the pattern surface of the mask orthe exposure target surface of the photosensitive substrate is alignedrelative to said projection optical system based upon results of adetection performed in said detection step.
 76. An exposure methodaccording to claim 75, wherein: said prism is constituted of an opticalmaterial having a coefficient of thermal expansion equal to or lowerthan 1 ppm/K, which does not expand readily in heat.
 77. An exposuremethod for implementing projection exposure of a pattern formed at amask onto a photosensitive substrate via a projection optical system,comprising; a detection step in which the surface position of a patternsurface of the mask or an exposure target surface of the photosensitivesubstrate relative to said projection optical system is detected as asurface position of a detection target surface by employing a surfaceposition detection device that detects the surface position of thedetection target surface and includes; a projection system that projectsa light flux from a diagonal direction onto the detection target surfaceand includes a projection optical system provided to form a primaryimage of a specific pattern onto the detection target surface; alight-receiving system that receives a light flux having been reflectedat the detection target surface and includes a condenser optical systemprovided to form a secondary image of the specific pattern by condensingthe light flux having been reflected at the detection target surface anda detection unit provided to detect the secondary image of the specificpattern formed via said condenser optical system; and a means for lightflux deflection provided, at least, either in an optical path of saidprojection system or in an optical path of said light-receiving systemand having an even number of reflection surfaces to allow an incidentlight flux to exit at an angle that is not parallel to the incidentlight flux, which includes a prism having a pair of reflection surfacesthat are not parallel to each other and constituted of a low-dispersionoptical material with an Abbe number of 65 or higher; to detect thesurface position of the detection target surface based upon an outputfrom said detection unit; and an alignment step in which the patternsurface of the mask or the exposure target surface of the photosensitivesubstrate is aligned relative to said projection optical system basedupon results of a detection performed in said detection step.
 78. Anexposure method according to claim 77, wherein: said prism isconstituted of an optical material having a coefficient of thermalexpansion equal to or lower than 1 ppm/K, which does not expand readilyin heat.
 79. An exposure method for implementing projection exposure ofa pattern formed at a mask onto a photosensitive substrate via aprojection optical system, comprising; a detection step in which thesurface position of a pattern surface of the mask or an exposure targetsurface of the photosensitive substrate relative to said projectionoptical system is detected as a surface position of a detection targetsurface by employing a surface position detection device that detectsthe surface position of the detection target surface and includes; aprojection system that projects a light flux from a diagonal directiononto the detection target surface and includes a projection opticalsystem provided to form a primary image of a specific pattern onto thedetection target surface; a light-receiving system that receives a lightflux having been reflected at the detection target surface and includesa condenser optical system provided to form a secondary image of thespecific pattern by condensing the light flux having been reflected atthe detection target surface and a detection unit provided to detect thesecondary image of the specific pattern formed via said condenseroptical system; and a means for light flux deflection provided, atleast, either in an optical path of said projection system or in anoptical path of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux which includes a prismhaving a pair of reflection surfaces that are not parallel to eachother, a first transmission surface through which the incident lightflux is transmitted, a first reflection surface at which the light fluxhaving been transmitted through said first transmission surface andpropagated through the inside of said prism is reflected, a secondreflection surface at which the light flux having been reflected at saidfirst reflection surface and propagated through the inside of said primis reflected along an optical path intersecting the optical path of thelight flux having been transmitted through said first transmissionsurface and a second transmission surface through which the light fluxhaving been reflected at said second reflection surface and propagatedthrough the inside of said prism is transmitted; to detect the surfaceposition of the detection target surface based upon an output from saiddetection unit; and an alignment step in which the pattern surface ofthe mask or the exposure target surface of the photosensitive substrateis aligned relative to said projection optical system based upon resultsof a detection performed in said detection step.
 80. An exposure methodaccording to claim 79, wherein: said prism is constituted of an opticalmaterial having a coefficient of thermal expansion equal to or lowerthan 1 ppm/K, which does not expand readily in heat.
 81. An exposuremethod for implementing projection exposure of a pattern formed at amask onto a photosensitive substrate via a projection optical system,comprising; a detection step in which the surface position of a patternsurface of the mask or an exposure target surface of the photosensitivesubstrate relative to said projection optical system is detected as asurface position of a detection target surface by employing a surfaceposition detection device that detects the surface position of thedetection target surface and includes; a projection system that projectsa light flux from a diagonal direction onto the detection target surfaceand includes a projection optical system provided to form a primaryimage of a specific pattern onto the detection target surface; alight-receiving system that receives a light flux having been reflectedat the detection target surface and includes a condenser optical systemprovided to form a secondary image of the specific pattern by condensingthe light flux having been reflected at the detection target surface anda detection unit provided to detect the secondary image of the specificpattern formed via said condenser optical system; and a means for lightflux deflection provided, at least, either in an optical path of saidprojection system or in an optical path of said light-receiving systemand having an even number of reflection surfaces to allow an incidentlight flux to exit at an angle that is not parallel to the incidentlight flux, which includes a prism having a pair of reflection surfacesthat are not parallel to each other, a first transmission surfacethrough which the incident light flux is transmitted, a first reflectionsurface at which the light flux having been transmitted through saidfirst transmission surface and propagated through the inside of saidprism is reflected, a second reflection surface at which the light fluxhaving been reflected at said first reflection surface and propagatedthrough the inside of said prim is reflected along an optical pathintersecting the optical path of the light flux having been transmittedthrough said first transmission surface and a second transmissionsurface through which the light flux having been reflected at saidsecond reflection surface and propagated through the inside of saidprism is transmitted, and constituted of a low-dispersion opticalmaterial with an Abbe number of 65 or higher; to detect the surfaceposition of the detection target surface based upon an output from saiddetection unit; and an alignment step in which the pattern surface ofthe mask or the exposure target surface of the photosensitive substrateis aligned relative to said projection optical system based upon resultsof a detection performed in said detection step.
 82. An exposure methodaccording to claim 81, wherein: said prism is constituted of an opticalmaterial having a coefficient of thermal expansion equal to or lowerthan 1 ppm/K, which does not expand readily in heat.
 83. An exposuremethod for implementing projection exposure of a pattern formed at amask onto a photosensitive substrate via a projection optical system,comprising; a detection step in which the surface position of a patternsurface of the mask or an exposure target surface of the photosensitivesubstrate relative to said projection optical system is detected as asurface position of a detection target surface by employing a surfaceposition detection device that detects the surface position of thedetection target surface and includes; a projection system that projectsa light flux from a diagonal direction onto the detection target surfaceand includes a projection optical system provided to form a primaryimage of a specific pattern onto the detection target surface; alight-receiving system that receives a light flux having been reflectedat the detection target surface and includes a condenser optical systemprovided to form a secondary image of the specific pattern by condensingthe light flux having been reflected at the detection target surface anda detection unit provided to detect the secondary image of the specificpattern formed via said condenser optical system; and a means for lightflux deflection provided, at least, either in an optical path of saidprojection system or in an optical path of said light-receiving systemand having an even number of reflection surfaces to allow an incidentlight flux to exit at an angle that is not parallel to the incidentlight flux, which includes a prism having a pair of reflection surfacesthat are not parallel to each other, a first transmission surfacethrough which the incident light flux is transmitted, a first reflectionsurface at which the light flux having been transmitted through saidfirst transmission surface and propagated through the inside of saidprism is reflected, a second reflection surface at which the light fluxhaving been reflected at said first reflection surface and propagatedthrough the inside of said prim is reflected along an optical pathintersecting the optical path of the light flux having been transmittedthrough said first transmission surface and a second transmissionsurface through which the light flux having been reflected at saidsecond reflection surface and propagated through the inside of saidprism is transmitted, and the angle formed by said first reflectionsurface and said second reflection surface set within a range of 40° orgreater and less than 45°; to detect the surface position of thedetection target surface based upon an output from said detection unit;and an alignment step in which the pattern surface of the mask or theexposure target surface of the photosensitive substrate is alignedrelative to said projection optical system based upon results of adetection performed in said detection step.
 84. An exposure methodaccording to claim 83, wherein: said prism is constituted of an opticalmaterial having a coefficient of thermal expansion equal to or lowerthan 1 ppm/K, which does not expand readily in heat.
 85. An exposuremethod for implementing projection exposure of a pattern formed at amask onto a photosensitive substrate via a projection optical system,comprising; a detection step in which the surface position of a patternsurface of the mask or an exposure target surface of the photosensitivesubstrate relative to said projection optical system is detected as asurface position of a detection target surface by employing a surfaceposition detection device that detects the surface position of thedetection target surface and includes; a projection system that projectsa light flux from a diagonal direction onto the detection target surfaceand includes a projection optical system provided to form a primaryimage of a specific pattern onto the detection target surface; alight-receiving system that receives a light flux having been reflectedat the detection target surface and includes a condenser optical systemprovided to form a secondary image of the specific pattern by condensingthe light flux having been reflected at the detection target surface anda detection unit provided to detect the secondary image of the specificpattern formed via said condenser optical system; and a means for lightflux deflection provided, at least, either in an optical path of saidprojection system or in an optical path of said light-receiving systemand having an even number of reflection surfaces to allow an incidentlight flux to exit at an angle that is not parallel to the incidentlight flux, which includes a prism having a pair of reflection surfacesthat are not parallel to each other, a first transmission surfacethrough which the incident light flux is transmitted, a first reflectionsurface at which the light flux having been transmitted through saidfirst transmission surface and propagated through the inside of saidprism is reflected, a second reflection surface at which the light fluxhaving been reflected at said first reflection surface and propagatedthrough the inside of said prim is reflected along an optical pathintersecting the optical path of the light flux having been transmittedthrough said first transmission surface and a second transmissionsurface through which the light flux having been reflected at saidsecond reflection surface and propagated through the inside of saidprism is transmitted, and the angle formed by said first reflectionsurface and said second reflection surface set within a range of 40° orgreater and less than 45° and said prism is constituted of alow-dispersion optical material with an Abbe number of 65 or higher; todetect the surface position of the detection target surface based uponan output from said detection unit; and an alignment step in which thepattern surface of the mask or the exposure target surface of thephotosensitive substrate is aligned relative to said projection opticalsystem based upon results of a detection performed in said detectionstep.
 86. An exposure method according to claim 85, wherein: said prismis constituted of an optical material having a coefficient of thermalexpansion equal to or lower than 1 ppm/K, which does not expand readilyin heat.
 87. An exposure method for implementing projection exposure ofa pattern formed at a mask onto a photosensitive substrate via aprojection optical system, comprising; a detection step in which thesurface position of a pattern surface of the mask or an exposure targetsurface of the photosensitive substrate relative to said projectionoptical system is detected as a surface position of a detection targetsurface by employing a surface position detection device that detectsthe surface position of the detection target surface and includes; aprojection system that projects a light flux from a diagonal directiononto the detection target surface; a light-receiving system thatreceives a light flux having been reflected at the detection targetsurface; and a means for light flux deflection provided, at least,either in an optical path of said projection system or in an opticalpath of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux, which includes a pairof reflection mirrors that are not parallel to each other and holdingmembers each provided to interfit with and hold one of said pair ofreflecting mirrors; to detect the surface position of the detectiontarget surface based upon an output from said light-receiving system;and an alignment step in which the pattern surface of the mask or theexposure target surface of the photosensitive substrate is alignedrelative to said projection optical system based upon results of adetection performed in said detection step.
 88. An exposure methodaccording to claim 87, wherein: said holding members are constituted ofan optical material having a coefficient of thermal expansion equal toor lower than 1 ppm/K, which does not expand readily in heat.
 89. Anexposure method for implementing projection exposure of a pattern formedat a mask onto a photosensitive substrate via a projection opticalsystem, comprising; a detection step in which the surface position of apattern surface of the mask or an exposure target surface of thephotosensitive substrate relative to said projection optical system isdetected as a surface position of a detection target surface byemploying a surface position detection device that detects the surfaceposition of the detection target surface and includes; a projectionsystem that projects a light flux from a diagonal direction onto thedetection target surface and includes a projection optical systemprovided to form a primary image of a specific pattern onto thedetection target surface; a light-receiving system that receives a lightflux having been reflected at the detection target surface and includesa condenser optical system provided to form a secondary image of thespecific pattern by condensing the light flux having been reflected atthe detection target surface and a detection unit provided to detect thesecondary image of the specific pattern formed via said condenseroptical system; and a means for light flux deflection provided, atleast, either in an optical path of said projection system or in anoptical path of said light-receiving system and having an even number ofreflection surfaces to allow an incident light flux to exit at an anglethat is not parallel to the incident light flux, which includes a pairof reflection mirrors that are not parallel to each other and holdingmembers each provided to interfit with and hold one of said pair ofreflecting mirrors; to detect the surface position of the detectiontarget surface based upon an output from said detection unit; and analignment step in which the pattern surface of the mask or the exposuretarget surface of the photosensitive substrate is aligned relative tosaid projection optical system based upon results of a detectionperformed in said detection step.
 90. An exposure method according toclaim 89, wherein: said holding members are constituted of an opticalmaterial having a coefficient of thermal expansion equal to or lowerthan 1 ppm/K, which does not expand readily in heat.